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I'd like to traverse a JSON object tree, but cannot find any library for that. It doesn't seem difficult but it feels like reinventing the wheel.
In XML there are so many tutorials showing how to traverse an XML tree with DOM :(
If you think jQuery is kind of overkill for such a primitive task, you could do something like that:
//your object
var o = {
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
};
//called with every property and its value
function process(key,value) {
console.log(key + " : "+value);
}
function traverse(o,func) {
for (var i in o) {
func.apply(this,[i,o[i]]);
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
traverse(o[i],func);
}
}
}
//that's all... no magic, no bloated framework
traverse(o,process);
A JSON object is simply a Javascript object. That's actually what JSON stands for: JavaScript Object Notation. So you'd traverse a JSON object however you'd choose to "traverse" a Javascript object in general.
In ES2017 you would do:
Object.entries(jsonObj).forEach(([key, value]) => {
// do something with key and val
});
You can always write a function to recursively descend into the object:
function traverse(jsonObj) {
if( jsonObj !== null && typeof jsonObj == "object" ) {
Object.entries(jsonObj).forEach(([key, value]) => {
// key is either an array index or object key
traverse(value);
});
}
else {
// jsonObj is a number or string
}
}
This should be a good starting point. I highly recommend using modern javascript methods for such things, since they make writing such code much easier.
function traverse(o) {
for (var i in o) {
if (!!o[i] && typeof(o[i])=="object") {
console.log(i, o[i]);
traverse(o[i]);
} else {
console.log(i, o[i]);
}
}
}
There's a new library for traversing JSON data with JavaScript that supports many different use cases.
https://npmjs.org/package/traverse
https://github.com/substack/js-traverse
It works with all kinds of JavaScript objects. It even detects cycles.
It provides the path of each node, too.
Original Simplified Answer
For a newer way to do it if you don't mind dropping IE and mainly supporting more current browsers (check kangax's es6 table for compatibility). You can use es2015 generators for this. I've updated #TheHippo's answer accordingly. Of course if you really want IE support you can use the babel JavaScript transpiler.
// Implementation of Traverse
function* traverse(o, path=[]) {
for (var i in o) {
const itemPath = path.concat(i);
yield [i,o[i],itemPath,o];
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
yield* traverse(o[i], itemPath);
}
}
}
// Traverse usage:
//that's all... no magic, no bloated framework
for(var [key, value, path, parent] of traverse({
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
})) {
// do something here with each key and value
console.log(key, value, path, parent);
}
If you want only own enumerable properties (basically non-prototype chain properties) you can change it to iterate using Object.keys and a for...of loop instead:
function* traverse(o,path=[]) {
for (var i of Object.keys(o)) {
const itemPath = path.concat(i);
yield [i,o[i],itemPath,o];
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
yield* traverse(o[i],itemPath);
}
}
}
//that's all... no magic, no bloated framework
for(var [key, value, path, parent] of traverse({
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
})) {
// do something here with each key and value
console.log(key, value, path, parent);
}
EDIT: This edited answer solves infinite looping traversals.
Stopping Pesky Infinite Object Traversals
This edited answer still provides one of the added benefits of my original answer which allows you to use the provided generator function in order to use a cleaner and simple iterable interface (think using for of loops as in for(var a of b) where b is an iterable and a is an element of the iterable). By using the generator function along with being a simpler api it also helps with code reuse by making it so you don't have to repeat the iteration logic everywhere you want to iterate deeply on an object's properties and it also makes it possible to break out of the loop if you would like to stop iteration earlier.
One thing that I notice that has not been addressed and that isn't in my original answer is that you should be careful traversing arbitrary (i.e. any "random" set of) objects, because JavaScript objects can be self referencing. This creates the opportunity to have infinite looping traversals. Unmodified JSON data however cannot be self referencing, so if you are using this particular subset of JS objects you don't have to worry about infinite looping traversals and you can refer to my original answer or other answers. Here is an example of a non-ending traversal (note it is not a runnable piece of code, because otherwise it would crash your browser tab).
Also in the generator object in my edited example I opted to use Object.keys instead of for in which iterates only non-prototype keys on the object. You can swap this out yourself if you want the prototype keys included. See my original answer section below for both implementations with Object.keys and for in.
Worse - This will infinite loop on self-referential objects:
function* traverse(o, path=[]) {
for (var i of Object.keys(o)) {
const itemPath = path.concat(i);
yield [i,o[i],itemPath, o];
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
yield* traverse(o[i], itemPath);
}
}
}
//your object
var o = {
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
};
// this self-referential property assignment is the only real logical difference
// from the above original example which ends up making this naive traversal
// non-terminating (i.e. it makes it infinite loop)
o.o = o;
//that's all... no magic, no bloated framework
for(var [key, value, path, parent] of traverse(o)) {
// do something here with each key and value
console.log(key, value, path, parent);
}
To save yourself from this you can add a set within a closure, so that when the function is first called it starts to build a memory of the objects it has seen and does not continue iteration once it comes across an already seen object. The below code snippet does that and thus handles infinite looping cases.
Better - This will not infinite loop on self-referential objects:
function* traverse(o) {
const memory = new Set();
function * innerTraversal (o, path=[]) {
if(memory.has(o)) {
// we've seen this object before don't iterate it
return;
}
// add the new object to our memory.
memory.add(o);
for (var i of Object.keys(o)) {
const itemPath = path.concat(i);
yield [i,o[i],itemPath, o];
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
yield* innerTraversal(o[i], itemPath);
}
}
}
yield* innerTraversal(o);
}
//your object
var o = {
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
};
/// this self-referential property assignment is the only real logical difference
// from the above original example which makes more naive traversals
// non-terminating (i.e. it makes it infinite loop)
o.o = o;
console.log(o);
//that's all... no magic, no bloated framework
for(var [key, value, path, parent] of traverse(o)) {
// do something here with each key and value
console.log(key, value, path, parent);
}
EDIT: All above examples in this answer have been edited to include a new path variable yielded from the iterator as per #supersan's request. The path variable is an array of strings where each string in the array represents each key that was accessed to get to the resulting iterated value from the original source object. The path variable can be fed into lodash's get function/method. Or you could write your own version of lodash's get which handles only arrays like so:
function get (object, path) {
return path.reduce((obj, pathItem) => obj ? obj[pathItem] : undefined, object);
}
const example = {a: [1,2,3], b: 4, c: { d: ["foo"] }};
// these paths exist on the object
console.log(get(example, ["a", "0"]));
console.log(get(example, ["c", "d", "0"]));
console.log(get(example, ["b"]));
// these paths do not exist on the object
console.log(get(example, ["e", "f", "g"]));
console.log(get(example, ["b", "f", "g"]));
You could also make a set function like so:
function set (object, path, value) {
const obj = path.slice(0,-1).reduce((obj, pathItem) => obj ? obj[pathItem] : undefined, object)
if(obj && obj[path[path.length - 1]]) {
obj[path[path.length - 1]] = value;
}
return object;
}
const example = {a: [1,2,3], b: 4, c: { d: ["foo"] }};
// these paths exist on the object
console.log(set(example, ["a", "0"], 2));
console.log(set(example, ["c", "d", "0"], "qux"));
console.log(set(example, ["b"], 12));
// these paths do not exist on the object
console.log(set(example, ["e", "f", "g"], false));
console.log(set(example, ["b", "f", "g"], null));
EDIT Sep. 2020: I added a parent for quicker access of the previous object. This could allow you to more quickly build a reverse traverser. Also you could always modify the traversal algorithm to do breadth first search instead of depth first which is actually probably more predictable in fact here's a TypeScript version with Breadth First Search. Since this is a JavaScript question I'll put the JS version here:
var TraverseFilter;
(function (TraverseFilter) {
/** prevents the children from being iterated. */
TraverseFilter["reject"] = "reject";
})(TraverseFilter || (TraverseFilter = {}));
function* traverse(o) {
const memory = new Set();
function* innerTraversal(root) {
const queue = [];
queue.push([root, []]);
while (queue.length > 0) {
const [o, path] = queue.shift();
if (memory.has(o)) {
// we've seen this object before don't iterate it
continue;
}
// add the new object to our memory.
memory.add(o);
for (var i of Object.keys(o)) {
const item = o[i];
const itemPath = path.concat([i]);
const filter = yield [i, item, itemPath, o];
if (filter === TraverseFilter.reject)
continue;
if (item !== null && typeof item === "object") {
//going one step down in the object tree!!
queue.push([item, itemPath]);
}
}
}
}
yield* innerTraversal(o);
}
//your object
var o = {
foo: "bar",
arr: [1, 2, 3],
subo: {
foo2: "bar2"
}
};
/// this self-referential property assignment is the only real logical difference
// from the above original example which makes more naive traversals
// non-terminating (i.e. it makes it infinite loop)
o.o = o;
//that's all... no magic, no bloated framework
for (const [key, value, path, parent] of traverse(o)) {
// do something here with each key and value
console.log(key, value, path, parent);
}
Depends on what you want to do. Here's an example of traversing a JavaScript object tree, printing keys and values as it goes:
function js_traverse(o) {
var type = typeof o
if (type == "object") {
for (var key in o) {
print("key: ", key)
js_traverse(o[key])
}
} else {
print(o)
}
}
js> foobar = {foo: "bar", baz: "quux", zot: [1, 2, 3, {some: "hash"}]}
[object Object]
js> js_traverse(foobar)
key: foo
bar
key: baz
quux
key: zot
key: 0
1
key: 1
2
key: 2
3
key: 3
key: some
hash
If you're traversing an actual JSON string then you can use a reviver function.
function traverse (json, callback) {
JSON.parse(json, function (key, value) {
if (key !== '') {
callback.call(this, key, value)
}
return value
})
}
traverse('{"a":{"b":{"c":{"d":1}},"e":{"f":2}}}', function (key, value) {
console.log(arguments)
})
When traversing an object:
function traverse (obj, callback, trail) {
trail = trail || []
Object.keys(obj).forEach(function (key) {
var value = obj[key]
if (Object.getPrototypeOf(value) === Object.prototype) {
traverse(value, callback, trail.concat(key))
} else {
callback.call(obj, key, value, trail)
}
})
}
traverse({a: {b: {c: {d: 1}}, e: {f: 2}}}, function (key, value, trail) {
console.log(arguments)
})
I wanted to use the perfect solution of #TheHippo in an anonymous function, without use of process and trigger functions. The following worked for me, sharing for novice programmers like myself.
(function traverse(o) {
for (var i in o) {
console.log('key : ' + i + ', value: ' + o[i]);
if (o[i] !== null && typeof(o[i])=="object") {
//going on step down in the object tree!!
traverse(o[i]);
}
}
})
(json);
Most Javascript engines do not optimize tail recursion (this might not be an issue if your JSON isn't deeply nested), but I usually err on the side of caution and do iteration instead, e.g.
function traverse(o, fn) {
const stack = [o]
while (stack.length) {
const obj = stack.shift()
Object.keys(obj).forEach((key) => {
fn(key, obj[key], obj)
if (obj[key] instanceof Object) {
stack.unshift(obj[key])
return
}
})
}
}
const o = {
name: 'Max',
legal: false,
other: {
name: 'Maxwell',
nested: {
legal: true
}
}
}
const fx = (key, value, obj) => console.log(key, value)
traverse(o, fx)
My Script:
op_needed = [];
callback_func = function(val) {
var i, j, len;
results = [];
for (j = 0, len = val.length; j < len; j++) {
i = val[j];
if (i['children'].length !== 0) {
call_func(i['children']);
} else {
op_needed.push(i['rel_path']);
}
}
return op_needed;
};
Input JSON:
[
{
"id": null,
"name": "output",
"asset_type_assoc": [],
"rel_path": "output",
"children": [
{
"id": null,
"name": "output",
"asset_type_assoc": [],
"rel_path": "output/f1",
"children": [
{
"id": null,
"name": "v#",
"asset_type_assoc": [],
"rel_path": "output/f1/ver",
"children": []
}
]
}
]
}
]
Function Call:
callback_func(inp_json);
Output as per my Need:
["output/f1/ver"]
var test = {
depth00: {
depth10: 'string'
, depth11: 11
, depth12: {
depth20:'string'
, depth21:21
}
, depth13: [
{
depth22:'2201'
, depth23:'2301'
}
, {
depth22:'2202'
, depth23:'2302'
}
]
}
,depth01: {
depth10: 'string'
, depth11: 11
, depth12: {
depth20:'string'
, depth21:21
}
, depth13: [
{
depth22:'2201'
, depth23:'2301'
}
, {
depth22:'2202'
, depth23:'2302'
}
]
}
, depth02: 'string'
, dpeth03: 3
};
function traverse(result, obj, preKey) {
if(!obj) return [];
if (typeof obj == 'object') {
for(var key in obj) {
traverse(result, obj[key], (preKey || '') + (preKey ? '[' + key + ']' : key))
}
} else {
result.push({
key: (preKey || '')
, val: obj
});
}
return result;
}
document.getElementById('textarea').value = JSON.stringify(traverse([], test), null, 2);
<textarea style="width:100%;height:600px;" id="textarea"></textarea>
I've created library to traverse and edit deep nested JS objects. Check out API here: https://github.com/dominik791
You can also play with the library interactively using demo app:
https://dominik791.github.io/obj-traverse-demo/
Examples of usage:
You should always have root object which is the first parameter of each method:
var rootObj = {
name: 'rootObject',
children: [
{
'name': 'child1',
children: [ ... ]
},
{
'name': 'child2',
children: [ ... ]
}
]
};
The second parameter is always the name of property that holds nested objects. In above case it would be 'children'.
The third parameter is an object that you use to find object/objects that you want to find/modify/delete. For example if you're looking for object with id equal to 1, then you will pass { id: 1} as the third parameter.
And you can:
findFirst(rootObj, 'children', { id: 1 }) to find first object
with id === 1
findAll(rootObj, 'children', { id: 1 }) to find all objects
with id === 1
findAndDeleteFirst(rootObj, 'children', { id: 1 }) to delete first matching object
findAndDeleteAll(rootObj, 'children', { id: 1 }) to delete all matching objects
replacementObj is used as the last parameter in two last methods:
findAndModifyFirst(rootObj, 'children', { id: 1 }, { id: 2, name: 'newObj'}) to change first found object with id === 1 to the { id: 2, name: 'newObj'}
findAndModifyAll(rootObj, 'children', { id: 1 }, { id: 2, name: 'newObj'}) to change all objects with id === 1 to the { id: 2, name: 'newObj'}
We use object-scan for many data processing tasks. It's powerful once you wrap your head around it. Here is how you could do basic traversal
// const objectScan = require('object-scan');
const obj = { foo: 'bar', arr: [1, 2, 3], subo: { foo2: 'bar2' } };
objectScan(['**'], {
reverse: false,
filterFn: ({ key, value }) => {
console.log(key, value);
}
})(obj);
// => [ 'foo' ] bar
// => [ 'arr', 0 ] 1
// => [ 'arr', 1 ] 2
// => [ 'arr', 2 ] 3
// => [ 'arr' ] [ 1, 2, 3 ]
// => [ 'subo', 'foo2' ] bar2
// => [ 'subo' ] { foo2: 'bar2' }
.as-console-wrapper {max-height: 100% !important; top: 0}
<script src="https://bundle.run/object-scan#13.8.0"></script>
Disclaimer: I'm the author of object-scan
This Will read All Nodes to a map.
function readJsonFile() {
let jsonString = getValueById("testDataContent");
let jsonObj = JSON.parse(jsonString);
let jsonElements = [];
jsonElements = traverse(jsonObj, jsonElements);
console.log(jsonElements)
}
function traverse(jsonObj, jsonElements) {
if (jsonObj !== null && typeof jsonObj == "object") {
Object.entries(jsonObj).forEach(([key, value]) => {
if (typeof value == "object") {
var obj = [];
let map = new Map();
map.set(key, traverse(value, obj))
jsonElements.push(map);
} else {
var obj = [];
obj.key = key;
obj.value = value;
jsonElements.push(obj);
}
});
} else {
}
return jsonElements;
}
You can get all keys / values and preserve the hierarchy with this
// get keys of an object or array
function getkeys(z){
var out=[];
for(var i in z){out.push(i)};
return out;
}
// print all inside an object
function allInternalObjs(data, name) {
name = name || 'data';
return getkeys(data).reduce(function(olist, k){
var v = data[k];
if(typeof v === 'object') { olist.push.apply(olist, allInternalObjs(v, name + '.' + k)); }
else { olist.push(name + '.' + k + ' = ' + v); }
return olist;
}, []);
}
// run with this
allInternalObjs({'a':[{'b':'c'},{'d':{'e':5}}],'f':{'g':'h'}}, 'ob')
This is a modification on (https://stackoverflow.com/a/25063574/1484447)
var localdata = [{''}]// Your json array
for (var j = 0; j < localdata.length; j++)
{$(localdata).each(function(index,item)
{
$('#tbl').append('<tr><td>' + item.FirstName +'</td></tr>);
}
The best solution for me was the following:
simple and without using any framework
var doSomethingForAll = function (arg) {
if (arg != undefined && arg.length > 0) {
arg.map(function (item) {
// do something for item
doSomethingForAll (item.subitem)
});
}
}
I am using _.isEqual that compares 2 array of objects (ex:10 properties each object), and it is working fine.
Now there are 2 properties (creation and deletion) that i need not to be a part of comparison.
Example:
var obj1 = {name: "James", age: 17, creation: "13-02-2016", deletion: "13-04-2016"}
var obj2 = {name: "Maria", age: 17, creation: "13-02-2016", deletion: "13-04-2016"}
// lodash method...
_.isEqual(firstArray, secondArray)
You can use omit() to remove specific properties in an object.
var result = _.isEqual(
_.omit(obj1, ['creation', 'deletion']),
_.omit(obj2, ['creation', 'deletion'])
);
var obj1 = {
name: "James",
age: 17,
creation: "13-02-2016",
deletion: "13-04-2016"
};
var obj2 = {
name: "Maria",
age: 17,
creation: "13-02-2016",
deletion: "13-04-2016"
};
var result = _.isEqual(
_.omit(obj1, ['creation', 'deletion']),
_.omit(obj2, ['creation', 'deletion'])
);
console.log(result);
<script src="https://cdn.jsdelivr.net/lodash/4.13.1/lodash.min.js"></script>
#ryeballar's answer is not great for large objects because you are creating a deep copy of each object every time you do the comparison.
It's better to use isEqualWith. For example, to ignore differences in the "creation" and "deletion" properties:
var result = _.isEqualWith(obj1, obj2, (value1, value2, key) => {
return key === "creation" || key === "deletion" ? true : undefined;
});
EDIT (important caveat pointed out in the comments): if objects have different numbers of keys, then isEqualWith considers them to be different, regadless of what your customizer does. Therefore do not use this approach if you want to ignore an optional property. Instead, consider using _.isMatch(), _.isMatchWith(), or #ryeballar's _.omit() approach.
Note that if you're writing for ES5 and earlier, you'll have to replace the arrow syntax (() => {) with function syntax (function() {)
_.omit creates deep copy of the object. If you need to exclude only root props it is better to create shallow copy using, for example, destructuring assignment:
const x = { a: 4, b: [1, 2], c: 'foo' }
const y = { a: 4, b: [1, 2], c: 'bar' }
const { c: xC, ...xWithoutC } = x
const { c: yC, ...yWithoutC } = y
_.isEqual(xWithoutC, yWithoutC) // true
xWithoutC.b === x.b // true, would be false if you use _.omit
Best way is not to create copies at all (TypeScript):
function deepEqual(
x?: object | null,
y?: object | null,
ignoreRootProps?: Set<string>
) {
if (x == null || y == null) return x === y
const keys = Object.keys(x)
if (!_.isEqual(keys, Object.keys(y)) return false
for (let key of keys) {
if (ignoreRootProps && ignoreRootProps.has(key)) continue
if (!_.isEqual(x[key], y[key])) return false
}
return true
}
You could map your array into a "cleaned" array, then compare those.
// Create a function, to do some cleaning of the objects.
var clean = function(obj) {
return {name: obj.name, age: obj.age};
};
// Create two new arrays, which are mapped, 'cleaned' copies of the original arrays.
var array1 = firstArray.map(clean);
var array2 = secondArray.map(clean);
// Compare the new arrays.
_.isEqual(array1, array2);
This has the downside that the clean function will need to be updated if the objects are expecting any new properties. It is possible to edit it so that it removes the two unwanted properties instead.
I see two options.
1) Make a second copy of each object that doesn't contain the creation or date.
2) Loop through all the properties and, assuming you know for certain that they both have the same properties, try something like this.
var x ={}
var y ={}
for (var property in x) {
if(property!="creation" || property!="deletion"){
if (x.hasOwnProperty(property)) {
compare(x[property], y[property])
}
}
}
Where compare() is some simple string or object comparison. If you are certain of the properties on one or both the objects, you can simplify this code a bit further, but this should work in most cases.
My final solution required a full comparison ignoring an optional property so the above solutions did not work.
I used a shallow clone to remove the keys I wanted to ignore from each object before comparing with isEqual:
const equalIgnoring = (newItems, originalItems) => newItems.length === originalItems.length
&& newItems.every((newItem, index) => {
const rest1 = { ...newItem };
delete rest1.creation;
delete rest1.deletion;
const rest2 = { ...originalItems[index] };
delete rest2.creation;
delete rest2.deletion;
return isEqual(rest1, rest2);
});
If you want to check a subset for each item in the array this works:
const equalIgnoringExtraKeys = (fullObjs, partialObjs) =>
fullObjs.length === partialObjs.length
&& fullObjs.every((fullObj, index) => isMatch(fullObj, partialObjs[index]));
If you also want to ignore a specific property and check subset:
const subsetIgnoringKeys = (fullObjs, partialObjs) =>
fullObjs.length === partialObjs.length
&& fullObjs.every((fullObj, index) => isMatchWith(
fullObj,
partialObjs[index],
(objValue, srcValue, key, object, source) => {
if (["creation", "deletion"].includes(key)) {
return true;
}
return undefined;
}
));
var addObjectResponse = [{
'SPO2': '222.00000',
'VitalGroupID': 1152,
'Temperature': 36.6666666666667,
'DateTimeTaken': '/Date(1301494335000-0400)/',
'UserID': 1,
'Height': 182.88,
'UserName': 'Admin',
'BloodPressureDiastolic': 80,
'Weight': 100909.090909091,
'TemperatureMethod': 'Oral',
'Resprate': 111,
'HeartRate': 111,
'BloodPressurePosition': 'Standing',
'VitalSite': 'Popliteal',
'VitalID': 1135,
'Laterality': 'Right',
'HeartRateRegularity': 'Regular',
'HeadCircumference': '',
'BloodPressureSystolic': 120,
'CuffSize': 'XL',
}];
How to rename the keys... like SPO2 into O2... there are such many objects in the array...
maybe something like this?
var i, len = addObjectResponse.length;
for (i = 0; i < len; i++) {
addObjectResponse[i]['O2'] = addObjectResponse[i]['SPO2'];
delete addObjectResponse[i]['SPO2'];
}
or
addObjectResponse = addObjectResponse.map(function (obj) {
obj['O2'] = obj['SP02'];
delete obj['S02'];
return obj;
});
or
for (let obj of addObjectResponse) {
obj['O2'] = obj['SP02'];
delete obj['S02'];
}
or
function renameProperty(obj, fromKey, toKey) {
obj[toKey] = obj[fromKey];
delete obj[fromKey];
}
addObjectResponse.forEach(obj => renameProperty(obj, 'SP02', 'O2'));
You cannot directly rename the properties. However, you can set new properties and unset the old ones, indirectly "renaming" them:
function rename(obj, oldName, newName) {
if(!obj.hasOwnProperty(oldName)) {
return false;
}
obj[newName] = obj[oldName];
delete obj[oldName];
return true;
}
Immutable key renaming in vanilla JS one-liner
This may not be the most efficient way to rename a key but I think it's interesting in certain ways:
It doesn't mutate the original objects
It takes one line of vanilla JavaScript
It demonstrates the use of modern syntax
No.1 may sometimes be needed if you still need to use the original array.
No.2 may be interesting considering the fact that some of the examples here have more than 30 lines of code.
No.3 may serve an educational purpose to demostrate some of the features of the language that are not used as often as they should, considering the fact how powerful and how widely supported they are.
If you create a mapping object like this:
const m = { SPO2: 'O2' };
then you'll be able to add more keys to rename in the future easily.
Now, can create a one-liner in vanilla JS:
const t = o => Object.assign(...Object.keys(o).map(k => ({ [m[k] || k]: o[k] })));
Let's say that you have an array of objects:
const a = [{
'SPO2': '222.00000',
'VitalGroupID': 1152,
}, {
'SPO2': '333.00000',
'VitalGroupID': 1153,
}, {
'SPO2': '444.00000',
'VitalGroupID': 1154,
}];
You can get a new array with a.map(t) like this:
console.log('Before:', a);
console.log('After:', a.map(t));
Your original objects are still intact in the original array.
I have created a nice function to rename properties names: https://github.com/meni181818/simpleCloneJS/blob/master/renameProperties.js
usage:
var renamedObj = renameProperties(sourceObject, {propName: 'propNEWname', anotherPropName: 'anotherPropNEWname'});
My function, also handles objects inside arrays so in your case you can do:
addObjectResponse = renameProperties(addObjectResponse, {SPO2: 'O2'});
DEMO
function renameProperties(sourceObj, replaceList, destObj) {
destObj = destObj || {};
each(sourceObj, function(key) {
if(sourceObj.hasOwnProperty(key)) {
if(sourceObj[key] instanceof Array) {
if(replaceList[key]) {
var newName = replaceList[key];
destObj[newName] = [];
renameProperties(sourceObj[key], replaceList, destObj[newName]);
} else if(!replaceList[key]) {
destObj[key] = [];
renameProperties(sourceObj[key], replaceList, destObj[key]);
}
} else if(typeof sourceObj[key] === 'object') {
if(replaceList[key]) {
var newName = replaceList[key];
destObj[newName] = {};
renameProperties(sourceObj[key], replaceList, destObj[newName]);
} else if(!replaceList[key]) {
destObj[key] = {};
renameProperties(sourceObj[key], replaceList, destObj[key]);
}
} else {
if(replaceList[key]) {
var newName = replaceList[key];
destObj[newName] = sourceObj[key];
} else if(!replaceList[key]) {
destObj[key] = sourceObj[key];
}
}
}
});
return destObj;
}
on line 3 in the function above, we using each() function. which is this:
function each(objOrArr, callBack) {
if(objOrArr instanceof Array) {
for(var i = 0; i < objOrArr.length; i++) {
callBack(i);
}
} else if(typeof objOrArr === 'object') {
for(var prop in objOrArr) {
// if the property really exist
if(objOrArr.hasOwnProperty(prop)) {
callBack(prop);
}
}
}
}
note: If you are using Jquery OR underscore.js Or another library that has 'each()' function, you can use it Instead. just replece to $.each (jquery) or _.each (underscore.js).
Ok, so there's two things you're doing here, iterating through an array and renaming properties of an object.
Firstly, to itterate you should generally be using the arrays map() function.
It's less error prone than using a for ( .. ) loop and slightly nicer than forEach(), I think.
A for ( .. ) loop will usually give you better performance (depending on the JS engine) but you need to be dealing with pretty massive array to notice (ie. maybe a ~10ms difference for 100k elements).
Secondly, to rename a object property, the obvious solution is to just set the new key and deleting the old.
This will work but won't always give you properties that behave exactly like the old one if a custom getter or setter has been defined.
If you're creating a generic helper function to do this kind of work you'd be better off using
Object.defineProperty() and
Object.getOwnPropertyDescriptor().
Putting this together we get:
function renameKeyInObjArray (array, oldKey, newKey) {
return array.map(function (obj) {
Object.defineProperty(obj, newKey, Object.getOwnPropertyDescriptor(obj, oldKey));
delete obj[oldKey];
return obj;
});
}
// Use our new function to process the array
renameKeyInObjArray(addObjectResponse, 'SPO2', 'O2');
This function updates the contents of the array by reference and also returns a reference to the array, so can be chained. It's also written in ES5.1 syntax so should run pretty much everywhere.
Here's one that works over an array of objects and takes a map of old object keys to new object keys.
I mostly copied the very nice code from here and just made it operate over arrays of objects rather than a single one.
Code
const renameKeys = (keysMap, objArr) =>
(renamedArr = objArr.map((obj) =>
Object.keys(obj).reduce(
(acc, key) => ({
...acc,
...{ [keysMap[key] || key]: obj[key] },
}),
{}
)
));
Example
renameKeys({ tWo: 'two', FreE: 'three' }, [
{ one: 1, tWo: 2, three: 3 },
{ one: 100, two: 200, FreE: 300 },
]);
[ { one: 1, two: 2, three: 3 }, { one: 100, two: 200, three: 300 } ]
You can add + delete (read the IE caveat);
var addObjectResponse = [{
'SPO2': '222.00000',
'VitalGroupID': 1152
}]
for (var k in addObjectResponse[0])
log(k)
>>SPO2
>>VitalGroupID
addObjectResponse[0]['O2'] = addObjectResponse[0]['SPO2']
delete addObjectResponse[0]['SPO2']
for (var k in addObjectResponse[0])
log(k)
>>VitalGroupID
>>O2
addObjectResponse[0]["O2"] = addObjectResponse[0]["SPO2"];
addObjectResponse[0]["SP02"] = null;
The [0] is necessary because addObjectResponse is set to an array with one element, which contains an object. Do you have any rules as to what keys will be renamed or how?
Edit: I misunderstood the OP, thinking that "many objects" referred to many keys in the object that need to be renamed, as opposed to many objects in the array that each need to have that one key renamed.
Instead of renaming this object key, you could create another object with proper names, like this:
var obj={wrongKeyName:'test'};
var obj2 = {}
obj2.rightKeyName = obj.wrongKeyName;
console.log(obj2);
A little late to the game here but how about something like this:
const newAddObjectResponse = addObjectResponse.map((obj) => {
const {SPO2: O2, ...rest} = obj
return {O2, ...rest}
})
If you want to replace your original array then you could do:
let addObjectResponse = [
{
SPO2: '222.00000',
VitalGroupID: 1152,
Temperature: 36.6666666666667,
DateTimeTaken: '/Date(1301494335000-0400)/',
UserID: 1,
Height: 182.88,
UserName: 'Admin',
BloodPressureDiastolic: 80,
Weight: 100909.090909091,
TemperatureMethod: 'Oral',
Resprate: 111,
HeartRate: 111,
BloodPressurePosition: 'Standing',
VitalSite: 'Popliteal',
VitalID: 1135,
Laterality: 'Right',
HeartRateRegularity: 'Regular',
HeadCircumference: '',
BloodPressureSystolic: 120,
CuffSize: 'XL',
},
]
addObjectResponse = addObjectResponse.map((obj) => {
const {SPO2: O2, ...rest} = obj
return {O2, ...rest}
})
This question already has answers here:
How can I merge properties of two JavaScript objects dynamically?
(69 answers)
Closed 1 year ago.
What’s the best/standard way of merging two associative arrays in JavaScript? Does everyone just do it by rolling their own for loop?
with jquery you can call $.extend
var obj1 = {a: 1, b: 2};
var obj2 = {a: 4, c: 110};
var obj3 = $.extend(obj1, obj2);
obj1 == obj3 == {a: 4, b: 2, c: 110} // Pseudo JS
(assoc. arrays are objects in js)
look here: http://api.jquery.com/jQuery.extend/
edit: Like rymo suggested, it's better to do it this way:
obj3 = $.extend({}, obj1, obj2);
obj3 == {a: 4, b: 2, c: 110}
As here obj1 (and obj2) remain unchanged.
edit2: In 2018 the way to do it is via Object.assign:
var obj3 = Object.assign({}, obj1, obj2);
obj3 === {a: 4, b: 2, c: 110} // Pseudo JS
If working with ES6 this can be achieved with the Spread Operator:
const obj3 = { ...obj1, ...obj2 };
Now in 2016 I would say the best/standard way is Object.assign()
Pure Javascript. No jQuery is needed.
obj1 = {a: 1, b: 2};
obj2 = {a: 4, c: 110};
obj3 = Object.assign({},obj1, obj2); // Object {a: 4, b: 2, c: 110}
More information, examples and polyfill here:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
This is how Prototype does it:
Object.extend = function(destination, source) {
for (var property in source) {
if (source.hasOwnProperty(property)) {
destination[property] = source[property];
}
}
return destination;
};
called as, for example:
var arr1 = { robert: "bobby", john: "jack" };
var arr2 = { elizabeth: "liz", jennifer: "jen" };
var shortnames = Object.extend(arr1,arr2);
EDIT: added hasOwnProperty() check as correctly pointed out by bucabay in comments
Keep it simple...
function mergeArray(array1,array2) {
for(item in array1) {
array2[item] = array1[item];
}
return array2;
}
Underscore also has an extend method:
Copy all of the properties in the source objects over to the
destination object. It's in-order, so the last source will override
properties of the same name in previous arguments.
_.extend(destination, *sources)
_.extend({name : 'moe'}, {age : 50});
=> {name : 'moe', age : 50}
In dojo, the 2-objects/arrays "merge" would be lang.mixin(destination, source) -- you can also mix multiple sources into one destination, etc -- see the mixin function's reference for details.
do you want to overwrite a property if the names are the same but the values are not?
And do you want to permanently change one of the original objects,
or do you want a new merged object returned?
function mergedObject(obj1, obj2, force){
for(var p in obj1) this[p]= obj1[p];
for(var p in obj2){
if(obj2.hasOwnProperty(p)){
if(force || this[p]=== undefined) this[p]= obj2[p];
else{
n= 2;
while(this[p+n]!== undefined)++n;
this[p+n]= obj2[p];
}
}
}
}
Rolling Your Own Extend/Mixin Function
function extend(objects) {
var args
, first = Array.prototype.slice.call(arguments, 0, 1)[0]
, second;
if (arguments.length > 1) {
second = Array.prototype.splice.call(arguments, 1, 1)[0];
for (var key in second) {
first[key] = second[key];
}
args = Array.prototype.slice.call(arguments, 0);
return extend.apply(this, args);
}
return first;
}
...
var briansDirections = {
step1: 'Remove pastry from wrapper.',
step2: 'Place pastry toaster.',
step3: 'Remove pastry from toaster and enjoy.',
};
extend(briansDirections, { step1: 'Toast Poptarts' }, { step2: 'Go ahead, toast \'em' }, { step3: 'Hey, are you sill reading this???' });
...
This simply extends a splat of objects, recursively. Also, note that this recursive function is TCO (Tail-Call Optimized) as its return is the last call to itself.
Additionally, you may want targeted properties. In this case, you may want to condense objects based upon id, quantity, or another property. This approach could have a small book written about it and requires object-juxtaposition and can get very complex. I've written a small library for this which is available upon request.
Hope this helps!
In Javascript there is no notion of
associative array, there are objects
The only way to merge two objects is
to loop for their properties and
copy pointers to their values that
are not primitive types and values
for primitive types to another
instance
In 2019 you have 2 good options:
Object assigning [doc]
const result = Object.assign({}, baseObject, updatingObject);
Object spreading [doc]
const result = { ...baseObject, ...updatingObject};
The first one tends to be safer, more standard and polyvalent. A good pros and cons here
Yahoo UI (YUI) also has a helper function for this:
http://developer.yahoo.com/yui/examples/yahoo/yahoo_merge.html
YAHOO.namespace('example');
YAHOO.example.set1 = { foo : "foo" };
YAHOO.example.set2 = { foo : "BAR", bar : "bar" };
YAHOO.example.set3 = { foo : "FOO", baz : "BAZ" };
var Ye = YAHOO.example;
var merged = YAHOO.lang.merge(Ye.set1, Ye.set2, Ye.set3);
jquery has a boolean for deep copy. You could do something like that:
MergeRecursive = function(arr1, arr2){
$.extend(true, arr1, arr2);
return arr1;
};
Also you can edit this function to support n-arrays to merge.
ArrayMergeRecursive = function(){
if(arguments.length < 2){
throw new Error("ArrayMergeRecursive: Please enter two or more objects to merge!");
}
var arr1=arguments[0];
for(var i=0; i<=arguments.length; i++ ){
$.extend(true, arr1, arguments[i]);
}
return arr1;
};
So now you can do
var arr1 = {'color': {'mycolor': 'red'}, 3: 5},
arr2 = {4: 10, 'color': {'favorite': 'green', 0: 'blue'}},
arr3 = ['Peter','Jhon','Demosthenes'],
results = ArrayMergeRecursive(arr1, arr2, arr3); // (arr1, arr2 ... arrN)
console.log("Result is:", results);
I needed a deep-object-merging. So all of the other answers didn't help me very much. _.extend and jQuery.extend do well, unless you have a recursive array like i do. But it ain't so bad, you can program it in five minutes:
var deep_merge = function (arr1, arr2) {
jQuery.each(arr2, function (index, element) {
if (typeof arr1[index] === "object" && typeof element === "object") {
arr1[index] = deep_merge(arr1[index], element);
} else if (typeof arr1[index] === "array" && typeof element === "array") {
arr1[index] = arr1[index].concat(element);
} else {
arr1[index] = element;
}
});
return arr1;
}
To merge arrays in jQuery what about $.merge?
var merged = $.merge([{id:3, value:'foo3'}], [{id:1, value:'foo1'}, {id:2, value:'foo2'}]);
merged[0].id == 3;
merged[0].value == 'foo3';
merged[1].id == 1;
merged[1].value == 'foo1';
merged[2].id == 2;
merged[2].value == 'foo2';
Recursive solution (extends also arrays of objects) + null checked
var addProps = function (original, props) {
if(!props) {
return original;
}
if (Array.isArray(original)) {
original.map(function (e) {
return addProps(e, props)
});
return original;
}
if (!original) {
original = {};
}
for (var property in props) {
if (props.hasOwnProperty(property)) {
original[property] = props[property];
}
}
return original;
};
Tests
console.log(addProps([{a: 2}, {z: 'ciao'}], {timestamp: 13}));
console.log(addProps({single: true}, {timestamp: 13}));
console.log(addProps({}, {timestamp: 13}));
console.log(addProps(null, {timestamp: 13}));
[ { a: 2, timestamp: 13 }, { z: 'ciao', timestamp: 13 } ]
{ single: true, timestamp: 13 }
{ timestamp: 13 }
{ timestamp: 13 }
Here is the best solution.
obj1.unshift.apply( obj1, obj2 );
Also, obj1 can grow inside a loop without any problem. (lets say obj2 is dynamic)
I'd like to traverse a JSON object tree, but cannot find any library for that. It doesn't seem difficult but it feels like reinventing the wheel.
In XML there are so many tutorials showing how to traverse an XML tree with DOM :(
If you think jQuery is kind of overkill for such a primitive task, you could do something like that:
//your object
var o = {
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
};
//called with every property and its value
function process(key,value) {
console.log(key + " : "+value);
}
function traverse(o,func) {
for (var i in o) {
func.apply(this,[i,o[i]]);
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
traverse(o[i],func);
}
}
}
//that's all... no magic, no bloated framework
traverse(o,process);
A JSON object is simply a Javascript object. That's actually what JSON stands for: JavaScript Object Notation. So you'd traverse a JSON object however you'd choose to "traverse" a Javascript object in general.
In ES2017 you would do:
Object.entries(jsonObj).forEach(([key, value]) => {
// do something with key and val
});
You can always write a function to recursively descend into the object:
function traverse(jsonObj) {
if( jsonObj !== null && typeof jsonObj == "object" ) {
Object.entries(jsonObj).forEach(([key, value]) => {
// key is either an array index or object key
traverse(value);
});
}
else {
// jsonObj is a number or string
}
}
This should be a good starting point. I highly recommend using modern javascript methods for such things, since they make writing such code much easier.
function traverse(o) {
for (var i in o) {
if (!!o[i] && typeof(o[i])=="object") {
console.log(i, o[i]);
traverse(o[i]);
} else {
console.log(i, o[i]);
}
}
}
There's a new library for traversing JSON data with JavaScript that supports many different use cases.
https://npmjs.org/package/traverse
https://github.com/substack/js-traverse
It works with all kinds of JavaScript objects. It even detects cycles.
It provides the path of each node, too.
Original Simplified Answer
For a newer way to do it if you don't mind dropping IE and mainly supporting more current browsers (check kangax's es6 table for compatibility). You can use es2015 generators for this. I've updated #TheHippo's answer accordingly. Of course if you really want IE support you can use the babel JavaScript transpiler.
// Implementation of Traverse
function* traverse(o, path=[]) {
for (var i in o) {
const itemPath = path.concat(i);
yield [i,o[i],itemPath,o];
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
yield* traverse(o[i], itemPath);
}
}
}
// Traverse usage:
//that's all... no magic, no bloated framework
for(var [key, value, path, parent] of traverse({
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
})) {
// do something here with each key and value
console.log(key, value, path, parent);
}
If you want only own enumerable properties (basically non-prototype chain properties) you can change it to iterate using Object.keys and a for...of loop instead:
function* traverse(o,path=[]) {
for (var i of Object.keys(o)) {
const itemPath = path.concat(i);
yield [i,o[i],itemPath,o];
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
yield* traverse(o[i],itemPath);
}
}
}
//that's all... no magic, no bloated framework
for(var [key, value, path, parent] of traverse({
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
})) {
// do something here with each key and value
console.log(key, value, path, parent);
}
EDIT: This edited answer solves infinite looping traversals.
Stopping Pesky Infinite Object Traversals
This edited answer still provides one of the added benefits of my original answer which allows you to use the provided generator function in order to use a cleaner and simple iterable interface (think using for of loops as in for(var a of b) where b is an iterable and a is an element of the iterable). By using the generator function along with being a simpler api it also helps with code reuse by making it so you don't have to repeat the iteration logic everywhere you want to iterate deeply on an object's properties and it also makes it possible to break out of the loop if you would like to stop iteration earlier.
One thing that I notice that has not been addressed and that isn't in my original answer is that you should be careful traversing arbitrary (i.e. any "random" set of) objects, because JavaScript objects can be self referencing. This creates the opportunity to have infinite looping traversals. Unmodified JSON data however cannot be self referencing, so if you are using this particular subset of JS objects you don't have to worry about infinite looping traversals and you can refer to my original answer or other answers. Here is an example of a non-ending traversal (note it is not a runnable piece of code, because otherwise it would crash your browser tab).
Also in the generator object in my edited example I opted to use Object.keys instead of for in which iterates only non-prototype keys on the object. You can swap this out yourself if you want the prototype keys included. See my original answer section below for both implementations with Object.keys and for in.
Worse - This will infinite loop on self-referential objects:
function* traverse(o, path=[]) {
for (var i of Object.keys(o)) {
const itemPath = path.concat(i);
yield [i,o[i],itemPath, o];
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
yield* traverse(o[i], itemPath);
}
}
}
//your object
var o = {
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
};
// this self-referential property assignment is the only real logical difference
// from the above original example which ends up making this naive traversal
// non-terminating (i.e. it makes it infinite loop)
o.o = o;
//that's all... no magic, no bloated framework
for(var [key, value, path, parent] of traverse(o)) {
// do something here with each key and value
console.log(key, value, path, parent);
}
To save yourself from this you can add a set within a closure, so that when the function is first called it starts to build a memory of the objects it has seen and does not continue iteration once it comes across an already seen object. The below code snippet does that and thus handles infinite looping cases.
Better - This will not infinite loop on self-referential objects:
function* traverse(o) {
const memory = new Set();
function * innerTraversal (o, path=[]) {
if(memory.has(o)) {
// we've seen this object before don't iterate it
return;
}
// add the new object to our memory.
memory.add(o);
for (var i of Object.keys(o)) {
const itemPath = path.concat(i);
yield [i,o[i],itemPath, o];
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
yield* innerTraversal(o[i], itemPath);
}
}
}
yield* innerTraversal(o);
}
//your object
var o = {
foo:"bar",
arr:[1,2,3],
subo: {
foo2:"bar2"
}
};
/// this self-referential property assignment is the only real logical difference
// from the above original example which makes more naive traversals
// non-terminating (i.e. it makes it infinite loop)
o.o = o;
console.log(o);
//that's all... no magic, no bloated framework
for(var [key, value, path, parent] of traverse(o)) {
// do something here with each key and value
console.log(key, value, path, parent);
}
EDIT: All above examples in this answer have been edited to include a new path variable yielded from the iterator as per #supersan's request. The path variable is an array of strings where each string in the array represents each key that was accessed to get to the resulting iterated value from the original source object. The path variable can be fed into lodash's get function/method. Or you could write your own version of lodash's get which handles only arrays like so:
function get (object, path) {
return path.reduce((obj, pathItem) => obj ? obj[pathItem] : undefined, object);
}
const example = {a: [1,2,3], b: 4, c: { d: ["foo"] }};
// these paths exist on the object
console.log(get(example, ["a", "0"]));
console.log(get(example, ["c", "d", "0"]));
console.log(get(example, ["b"]));
// these paths do not exist on the object
console.log(get(example, ["e", "f", "g"]));
console.log(get(example, ["b", "f", "g"]));
You could also make a set function like so:
function set (object, path, value) {
const obj = path.slice(0,-1).reduce((obj, pathItem) => obj ? obj[pathItem] : undefined, object)
if(obj && obj[path[path.length - 1]]) {
obj[path[path.length - 1]] = value;
}
return object;
}
const example = {a: [1,2,3], b: 4, c: { d: ["foo"] }};
// these paths exist on the object
console.log(set(example, ["a", "0"], 2));
console.log(set(example, ["c", "d", "0"], "qux"));
console.log(set(example, ["b"], 12));
// these paths do not exist on the object
console.log(set(example, ["e", "f", "g"], false));
console.log(set(example, ["b", "f", "g"], null));
EDIT Sep. 2020: I added a parent for quicker access of the previous object. This could allow you to more quickly build a reverse traverser. Also you could always modify the traversal algorithm to do breadth first search instead of depth first which is actually probably more predictable in fact here's a TypeScript version with Breadth First Search. Since this is a JavaScript question I'll put the JS version here:
var TraverseFilter;
(function (TraverseFilter) {
/** prevents the children from being iterated. */
TraverseFilter["reject"] = "reject";
})(TraverseFilter || (TraverseFilter = {}));
function* traverse(o) {
const memory = new Set();
function* innerTraversal(root) {
const queue = [];
queue.push([root, []]);
while (queue.length > 0) {
const [o, path] = queue.shift();
if (memory.has(o)) {
// we've seen this object before don't iterate it
continue;
}
// add the new object to our memory.
memory.add(o);
for (var i of Object.keys(o)) {
const item = o[i];
const itemPath = path.concat([i]);
const filter = yield [i, item, itemPath, o];
if (filter === TraverseFilter.reject)
continue;
if (item !== null && typeof item === "object") {
//going one step down in the object tree!!
queue.push([item, itemPath]);
}
}
}
}
yield* innerTraversal(o);
}
//your object
var o = {
foo: "bar",
arr: [1, 2, 3],
subo: {
foo2: "bar2"
}
};
/// this self-referential property assignment is the only real logical difference
// from the above original example which makes more naive traversals
// non-terminating (i.e. it makes it infinite loop)
o.o = o;
//that's all... no magic, no bloated framework
for (const [key, value, path, parent] of traverse(o)) {
// do something here with each key and value
console.log(key, value, path, parent);
}
Depends on what you want to do. Here's an example of traversing a JavaScript object tree, printing keys and values as it goes:
function js_traverse(o) {
var type = typeof o
if (type == "object") {
for (var key in o) {
print("key: ", key)
js_traverse(o[key])
}
} else {
print(o)
}
}
js> foobar = {foo: "bar", baz: "quux", zot: [1, 2, 3, {some: "hash"}]}
[object Object]
js> js_traverse(foobar)
key: foo
bar
key: baz
quux
key: zot
key: 0
1
key: 1
2
key: 2
3
key: 3
key: some
hash
If you're traversing an actual JSON string then you can use a reviver function.
function traverse (json, callback) {
JSON.parse(json, function (key, value) {
if (key !== '') {
callback.call(this, key, value)
}
return value
})
}
traverse('{"a":{"b":{"c":{"d":1}},"e":{"f":2}}}', function (key, value) {
console.log(arguments)
})
When traversing an object:
function traverse (obj, callback, trail) {
trail = trail || []
Object.keys(obj).forEach(function (key) {
var value = obj[key]
if (Object.getPrototypeOf(value) === Object.prototype) {
traverse(value, callback, trail.concat(key))
} else {
callback.call(obj, key, value, trail)
}
})
}
traverse({a: {b: {c: {d: 1}}, e: {f: 2}}}, function (key, value, trail) {
console.log(arguments)
})
I wanted to use the perfect solution of #TheHippo in an anonymous function, without use of process and trigger functions. The following worked for me, sharing for novice programmers like myself.
(function traverse(o) {
for (var i in o) {
console.log('key : ' + i + ', value: ' + o[i]);
if (o[i] !== null && typeof(o[i])=="object") {
//going on step down in the object tree!!
traverse(o[i]);
}
}
})
(json);
Most Javascript engines do not optimize tail recursion (this might not be an issue if your JSON isn't deeply nested), but I usually err on the side of caution and do iteration instead, e.g.
function traverse(o, fn) {
const stack = [o]
while (stack.length) {
const obj = stack.shift()
Object.keys(obj).forEach((key) => {
fn(key, obj[key], obj)
if (obj[key] instanceof Object) {
stack.unshift(obj[key])
return
}
})
}
}
const o = {
name: 'Max',
legal: false,
other: {
name: 'Maxwell',
nested: {
legal: true
}
}
}
const fx = (key, value, obj) => console.log(key, value)
traverse(o, fx)
My Script:
op_needed = [];
callback_func = function(val) {
var i, j, len;
results = [];
for (j = 0, len = val.length; j < len; j++) {
i = val[j];
if (i['children'].length !== 0) {
call_func(i['children']);
} else {
op_needed.push(i['rel_path']);
}
}
return op_needed;
};
Input JSON:
[
{
"id": null,
"name": "output",
"asset_type_assoc": [],
"rel_path": "output",
"children": [
{
"id": null,
"name": "output",
"asset_type_assoc": [],
"rel_path": "output/f1",
"children": [
{
"id": null,
"name": "v#",
"asset_type_assoc": [],
"rel_path": "output/f1/ver",
"children": []
}
]
}
]
}
]
Function Call:
callback_func(inp_json);
Output as per my Need:
["output/f1/ver"]
var test = {
depth00: {
depth10: 'string'
, depth11: 11
, depth12: {
depth20:'string'
, depth21:21
}
, depth13: [
{
depth22:'2201'
, depth23:'2301'
}
, {
depth22:'2202'
, depth23:'2302'
}
]
}
,depth01: {
depth10: 'string'
, depth11: 11
, depth12: {
depth20:'string'
, depth21:21
}
, depth13: [
{
depth22:'2201'
, depth23:'2301'
}
, {
depth22:'2202'
, depth23:'2302'
}
]
}
, depth02: 'string'
, dpeth03: 3
};
function traverse(result, obj, preKey) {
if(!obj) return [];
if (typeof obj == 'object') {
for(var key in obj) {
traverse(result, obj[key], (preKey || '') + (preKey ? '[' + key + ']' : key))
}
} else {
result.push({
key: (preKey || '')
, val: obj
});
}
return result;
}
document.getElementById('textarea').value = JSON.stringify(traverse([], test), null, 2);
<textarea style="width:100%;height:600px;" id="textarea"></textarea>
I've created library to traverse and edit deep nested JS objects. Check out API here: https://github.com/dominik791
You can also play with the library interactively using demo app:
https://dominik791.github.io/obj-traverse-demo/
Examples of usage:
You should always have root object which is the first parameter of each method:
var rootObj = {
name: 'rootObject',
children: [
{
'name': 'child1',
children: [ ... ]
},
{
'name': 'child2',
children: [ ... ]
}
]
};
The second parameter is always the name of property that holds nested objects. In above case it would be 'children'.
The third parameter is an object that you use to find object/objects that you want to find/modify/delete. For example if you're looking for object with id equal to 1, then you will pass { id: 1} as the third parameter.
And you can:
findFirst(rootObj, 'children', { id: 1 }) to find first object
with id === 1
findAll(rootObj, 'children', { id: 1 }) to find all objects
with id === 1
findAndDeleteFirst(rootObj, 'children', { id: 1 }) to delete first matching object
findAndDeleteAll(rootObj, 'children', { id: 1 }) to delete all matching objects
replacementObj is used as the last parameter in two last methods:
findAndModifyFirst(rootObj, 'children', { id: 1 }, { id: 2, name: 'newObj'}) to change first found object with id === 1 to the { id: 2, name: 'newObj'}
findAndModifyAll(rootObj, 'children', { id: 1 }, { id: 2, name: 'newObj'}) to change all objects with id === 1 to the { id: 2, name: 'newObj'}
We use object-scan for many data processing tasks. It's powerful once you wrap your head around it. Here is how you could do basic traversal
// const objectScan = require('object-scan');
const obj = { foo: 'bar', arr: [1, 2, 3], subo: { foo2: 'bar2' } };
objectScan(['**'], {
reverse: false,
filterFn: ({ key, value }) => {
console.log(key, value);
}
})(obj);
// => [ 'foo' ] bar
// => [ 'arr', 0 ] 1
// => [ 'arr', 1 ] 2
// => [ 'arr', 2 ] 3
// => [ 'arr' ] [ 1, 2, 3 ]
// => [ 'subo', 'foo2' ] bar2
// => [ 'subo' ] { foo2: 'bar2' }
.as-console-wrapper {max-height: 100% !important; top: 0}
<script src="https://bundle.run/object-scan#13.8.0"></script>
Disclaimer: I'm the author of object-scan
This Will read All Nodes to a map.
function readJsonFile() {
let jsonString = getValueById("testDataContent");
let jsonObj = JSON.parse(jsonString);
let jsonElements = [];
jsonElements = traverse(jsonObj, jsonElements);
console.log(jsonElements)
}
function traverse(jsonObj, jsonElements) {
if (jsonObj !== null && typeof jsonObj == "object") {
Object.entries(jsonObj).forEach(([key, value]) => {
if (typeof value == "object") {
var obj = [];
let map = new Map();
map.set(key, traverse(value, obj))
jsonElements.push(map);
} else {
var obj = [];
obj.key = key;
obj.value = value;
jsonElements.push(obj);
}
});
} else {
}
return jsonElements;
}
You can get all keys / values and preserve the hierarchy with this
// get keys of an object or array
function getkeys(z){
var out=[];
for(var i in z){out.push(i)};
return out;
}
// print all inside an object
function allInternalObjs(data, name) {
name = name || 'data';
return getkeys(data).reduce(function(olist, k){
var v = data[k];
if(typeof v === 'object') { olist.push.apply(olist, allInternalObjs(v, name + '.' + k)); }
else { olist.push(name + '.' + k + ' = ' + v); }
return olist;
}, []);
}
// run with this
allInternalObjs({'a':[{'b':'c'},{'d':{'e':5}}],'f':{'g':'h'}}, 'ob')
This is a modification on (https://stackoverflow.com/a/25063574/1484447)
var localdata = [{''}]// Your json array
for (var j = 0; j < localdata.length; j++)
{$(localdata).each(function(index,item)
{
$('#tbl').append('<tr><td>' + item.FirstName +'</td></tr>);
}
The best solution for me was the following:
simple and without using any framework
var doSomethingForAll = function (arg) {
if (arg != undefined && arg.length > 0) {
arg.map(function (item) {
// do something for item
doSomethingForAll (item.subitem)
});
}
}