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Accessing nested JavaScript objects and arrays by string path
(44 answers)
Closed 7 years ago.
I'm temporarily stuck with what appears to be a very simple JavaScript problem, but maybe I'm just missing the right search keywords!
Say we have an object
var r = { a:1, b: {b1:11, b2: 99}};
There are several ways to access the 99:
r.b.b2
r['b']['b2']
What I want is to be able to define a string
var s = "b.b2";
and then access the 99 using
r.s or r[s] //(which of course won't work)
One way is to write a function for it that splits the string on dot and maybe recursively/iteratively gets the property. But is there any simpler/more efficient way? Anything useful in any of the jQuery APIs here?
Here's a naive function I wrote a while ago, but it works for basic object properties:
function getDescendantProp(obj, desc) {
var arr = desc.split(".");
while(arr.length && (obj = obj[arr.shift()]));
return obj;
}
console.log(getDescendantProp(r, "b.b2"));
//-> 99
Although there are answers that extend this to "allow" array index access, that's not really necessary as you can just specify numerical indexes using dot notation with this method:
getDescendantProp({ a: [ 1, 2, 3 ] }, 'a.2');
//-> 3
split and reduce while passing the object as the initalValue
Update
(thanks to comment posted by TeChn4K)
With ES6 syntax, it is even shorter
var r = { a:1, b: {b1:11, b2: 99}};
var s = "b.b2";
var value = s.split('.').reduce((a, b) => a[b], r);
console.log(value);
Old version
var r = { a:1, b: {b1:11, b2: 99}};
var s = "b.b2";
var value = s.split('.').reduce(function(a, b) {
return a[b];
}, r);
console.log(value);
You can use lodash get() and set() methods.
Getting
var object = { 'a': [{ 'b': { 'c': 3 } }] };
_.get(object, 'a[0].b.c');
// → 3
Setting
var object = { 'a': [{ 'b': { 'c': 3 } }] };
_.set(object, 'a[0].b.c', 4);
console.log(object.a[0].b.c);
// → 4
If it's possible in your scenario that you could put the entire array variable you're after into a string you could use the eval() function.
var r = { a:1, b: {b1:11, b2: 99}};
var s = "r.b.b2";
alert(eval(s)); // 99
I can feel people reeling in horror
Extending #JohnB's answer, I added a setter value as well. Check out the plunkr at
http://plnkr.co/edit/lo0thC?p=preview
function getSetDescendantProp(obj, desc, value) {
var arr = desc ? desc.split(".") : [];
while (arr.length && obj) {
var comp = arr.shift();
var match = new RegExp("(.+)\\[([0-9]*)\\]").exec(comp);
// handle arrays
if ((match !== null) && (match.length == 3)) {
var arrayData = {
arrName: match[1],
arrIndex: match[2]
};
if (obj[arrayData.arrName] !== undefined) {
if (typeof value !== 'undefined' && arr.length === 0) {
obj[arrayData.arrName][arrayData.arrIndex] = value;
}
obj = obj[arrayData.arrName][arrayData.arrIndex];
} else {
obj = undefined;
}
continue;
}
// handle regular things
if (typeof value !== 'undefined') {
if (obj[comp] === undefined) {
obj[comp] = {};
}
if (arr.length === 0) {
obj[comp] = value;
}
}
obj = obj[comp];
}
return obj;
}
This is the simplest i could do:
var accessProperties = function(object, string){
var explodedString = string.split('.');
for (i = 0, l = explodedString.length; i<l; i++){
object = object[explodedString[i]];
}
return object;
}
var r = { a:1, b: {b1:11, b2: 99}};
var s = "b.b2";
var o = accessProperties(r, s);
alert(o);//99
you could also do
var s = "['b'].b2";
var num = eval('r'+s);
Here is an extension of Andy E's code, that recurses into arrays and returns all values:
function GetDescendantProps(target, pathString) {
var arr = pathString.split(".");
while(arr.length && (target = target[arr.shift()])){
if (arr.length && target.length && target.forEach) { // handle arrays
var remainder = arr.join('.');
var results = [];
for (var i = 0; i < target.length; i++){
var x = this.GetDescendantProps(target[i], remainder);
if (x) results = results.concat(x);
}
return results;
}
}
return (target) ? [target] : undefined; //single result, wrap in array for consistency
}
So given this target:
var t =
{a:
{b: [
{'c':'x'},
{'not me':'y'},
{'c':'z'}
]
}
};
We get:
GetDescendantProps(t, "a.b.c") === ["x", "z"]; // true
I don't know a supported jQuery API function but I have this function:
var ret = data; // Your object
var childexpr = "b.b2"; // Your expression
if (childexpr != '') {
var childs = childexpr.split('.');
var i;
for (i = 0; i < childs.length && ret != undefined; i++) {
ret = ret[childs[i]];
}
}
return ret;
I've extended Andy E's answer, so that it can also handle arrays:
function getDescendantProp(obj, desc) {
var arr = desc.split(".");
//while (arr.length && (obj = obj[arr.shift()]));
while (arr.length && obj) {
var comp = arr.shift();
var match = new RegExp("(.+)\\[([0-9]*)\\]").exec(comp);
if ((match !== null) && (match.length == 3)) {
var arrayData = { arrName: match[1], arrIndex: match[2] };
if (obj[arrayData.arrName] != undefined) {
obj = obj[arrayData.arrName][arrayData.arrIndex];
} else {
obj = undefined;
}
} else {
obj = obj[comp]
}
}
return obj;
}
There are probably more efficient ways to do the Regex, but it's compact.
You can now do stuff like:
var model = {
"m1": {
"Id": "22345",
"People": [
{ "Name": "John", "Numbers": ["07263", "17236", "1223"] },
{ "Name": "Jenny", "Numbers": ["2", "3", "6"] },
{ "Name": "Bob", "Numbers": ["12", "3333", "4444"] }
]
}
}
// Should give you "6"
var x = getDescendantProp(model, "m1.People[1].Numbers[2]");
Performance tests for Andy E's, Jason More's, and my own solution are available at http://jsperf.com/propertyaccessor. Please feel free to run tests using your own browser to add to the data collected.
The prognosis is clear, Andy E's solution is the fastest by far!
For anyone interested, here is the code for my solution to the original question.
function propertyAccessor(object, keys, array) {
/*
Retrieve an object property with a dot notation string.
#param {Object} object Object to access.
#param {String} keys Property to access using 0 or more dots for notation.
#param {Object} [array] Optional array of non-dot notation strings to use instead of keys.
#return {*}
*/
array = array || keys.split('.')
if (array.length > 1) {
// recurse by calling self
return propertyAccessor(object[array.shift()], null, array)
} else {
return object[array]
}
}
Short answer: No, there is no native .access function like you want it. As you correctly mentioned, you would have to define your own function which splits the string and loops/checks over its parts.
Of course, what you always can do (even if its considered bad practice) is to use eval().
Like
var s = 'b.b2';
eval('r.' + s); // 99
Here is a a little better way then #andy's answer, where the obj (context) is optional, it falls back to window if not provided..
function getDescendantProp(desc, obj) {
obj = obj || window;
var arr = desc.split(".");
while (arr.length && (obj = obj[arr.shift()]));
return obj;
};
Let's say I have a Javascript associative array (a.k.a. hash, a.k.a. dictionary):
var a = new Array();
a['b'] = 1;
a['z'] = 1;
a['a'] = 1;
How can I iterate over the keys in sorted order? If it helps simplify things, I don't even need the values (they're all just the number 1).
You can use the Object.keys built-in method:
var sorted_keys = Object.keys(a).sort()
(Note: this does not work in very old browsers not supporting EcmaScript5, notably IE6, 7 and 8. For detailed up-to-date statistics, see this table)
You cannot iterate over them directly, but you can find all the keys and then just sort them.
var a = new Array();
a['b'] = 1;
a['z'] = 1;
a['a'] = 1;
function keys(obj)
{
var keys = [];
for(var key in obj)
{
if(obj.hasOwnProperty(key))
{
keys.push(key);
}
}
return keys;
}
keys(a).sort(); // ["a", "b", "z"]
However there is no need to make the variable 'a' an array. You are really just using it as an object and should create it like this:
var a = {};
a["key"] = "value";
you could even prototype it onto object:
Object.prototype.iterateSorted = function(worker)
{
var keys = [];
for (var key in this)
{
if (this.hasOwnProperty(key))
keys.push(key);
}
keys.sort();
for (var i = 0; i < keys.length; i++)
{
worker(this[ keys[i] ]);
}
}
and the usage:
var myObj = { a:1, b:2 };
myObj.iterateSorted(function(value)
{
alert(value);
}
I agree with Swingley's answer, and I think it is an important point a lot of these more elaborate solutions are missing. If you are only concerned with the keys in the associative array and all the values are '1', then simply store the 'keys' as values in an array.
Instead of:
var a = { b:1, z:1, a:1 };
// relatively elaborate code to retrieve the keys and sort them
Use:
var a = [ 'b', 'z', 'a' ];
alert(a.sort());
The one drawback to this is that you can not determine whether a specific key is set as easily. See this answer to javascript function inArray for an answer to that problem. One issue with the solution presented is that a.hasValue('key') is going to be slightly slower than a['key']. That may or may not matter in your code.
There's no concise way to directly manipulate the "keys" of a Javascript object. It's not really designed for that. Do you have the freedom to put your data in something better than a regular object (or an Array, as your sample code suggests)?
If so, and if your question could be rephrased as "What dictionary-like object should I use if I want to iterate over the keys in sorted order?" then you might develop an object like this:
var a = {
keys : new Array(),
hash : new Object(),
set : function(key, value) {
if (typeof(this.hash[key]) == "undefined") { this.keys.push(key); }
this.hash[key] = value;
},
get : function(key) {
return this.hash[key];
},
getSortedKeys : function() {
this.keys.sort();
return this.keys;
}
};
// sample use
a.set('b',1);
a.set('z',1);
a.set('a',1);
var sortedKeys = a.getSortedKeys();
for (var i in sortedKeys) { print(sortedKeys[i]); }
If you have no control over the fact that the data is in a regular object, this utility would convert the regular object to your fully-functional dictionary:
a.importObject = function(object) {
for (var i in object) { this.set(i, object); }
};
This was a object definition (instead of a reusable constructor function) for simplicity; edit at will.
Get the keys in the first for loop, sort it, use the sorted result in the 2nd for loop.
var a = new Array();
a['b'] = 1;
a['z'] = 1;
a['a'] = 1;
var b = [];
for (k in a) b.push(k);
b.sort();
for (var i = 0; i < b.length; ++i) alert(b[i]);
You can use the keys function from the underscore.js library to get the keys, then the sort() array method to sort them:
var sortedKeys = _.keys(dict).sort();
The keys function in the underscore's source code:
// Retrieve the names of an object's properties.
// Delegates to **ECMAScript 5**'s native `Object.keys`
_.keys = nativeKeys || function(obj) {
if (obj !== Object(obj)) throw new TypeError('Invalid object');
var keys = [];
for (var key in obj) if (_.has(obj, key)) keys.push(key);
return keys;
};
// Shortcut function for checking if an object has a given property directly
// on itself (in other words, not on a prototype).
_.has = function(obj, key) {
return hasOwnProperty.call(obj, key);
};
<script type="text/javascript">
var a = {
b:1,
z:1,
a:1
}; // your JS Object
var keys = [];
for (key in a) {
keys.push(key);
}
keys.sort();
var i = 0;
var keyslen = keys.length;
var str = '';
//SORTED KEY ITERATION
while (i < keyslen) {
str += keys[i] + '=>' + a[keys[i]] + '\n';
++i;
}
alert(str);
/*RESULT:
a=>1
b=>1
z=>1
*/
</script>
var a = new Array();
a['b'] = 1;
a['z'] = 1;
a['a'] = 1;
var keys=Object.keys(a).sort();
for(var i=0,key=keys[0];i<keys.length;key=keys[++i]){
document.write(key+' : '+a[key]+'<br>');
}
I really like #luke-schafer's prototype idea, but also hear what he is saying about the issues with prototypes. What about using a simple function?
function sortKeysAndDo( obj, worker ) {
var keys = Object.keys(obj);
keys.sort();
for (var i = 0; i < keys.length; i++) {
worker(keys[i], obj[keys[i]]);
}
}
function show( key, value ) {
document.write( key + ' : ' + value +'<br>' );
}
var a = new Array();
a['b'] = 1;
a['z'] = 1;
a['a'] = 1;
sortKeysAndDo( a, show);
var my_object = { 'c': 3, 'a': 1, 'b': 2 };
sortKeysAndDo( my_object, show);
This seems to eliminate the issues with prototypes and still provide a sorted iterator for objects. I am not really a JavaScript guru, though, so I'd love to know if this solution has hidden flaws I missed.
My application has a large array of objects, which I stringify and save them to the disk. Unfortunately, when the objects in the array are manipulated, and sometimes replaced, the properties on the objects are listed in different orders (their creation order?). When I do JSON.stringify() on the array and save it, a diff shows the properties getting listed in different orders, which is annoying when trying to merge the data further with diff and merging tools.
Ideally I would like to sort the properties of the objects in alphabetical order prior to performing the stringify, or as part of the stringify operation. There is code for manipulating the array objects in many places, and altering these to always create properties in an explicit order would be difficult.
Suggestions would be most welcome!
A condensed example:
obj = {}; obj.name="X"; obj.os="linux";
JSON.stringify(obj);
obj = {}; obj.os="linux"; obj.name="X";
JSON.stringify(obj);
The output of these two stringify calls are different, and showing up in a diff of my data, but my application doesn't care about the ordering of properties. The objects are constructed in many ways and places.
The simpler, modern and currently browser supported approach is simply this:
JSON.stringify(sortMyObj, Object.keys(sortMyObj).sort());
However, this method does remove any nested objects that aren't referenced and does not apply to objects within arrays. You will want to flatten the sorting object as well if you want something like this output:
{"a":{"h":4,"z":3},"b":2,"c":1}
You can do that with this:
var flattenObject = function(ob) {
var toReturn = {};
for (var i in ob) {
if (!ob.hasOwnProperty(i)) continue;
if ((typeof ob[i]) == 'object') {
var flatObject = flattenObject(ob[i]);
for (var x in flatObject) {
if (!flatObject.hasOwnProperty(x)) continue;
toReturn[i + '.' + x] = flatObject[x];
}
} else {
toReturn[i] = ob[i];
}
}
return toReturn;
};
var myFlattenedObj = flattenObject(sortMyObj);
JSON.stringify(myFlattenedObj, Object.keys(myFlattenedObj).sort());
To do it programmatically with something you can tweak yourself, you need to push the object property names into an array, then sort the array alphabetically and iterate through that array (which will be in the right order) and select each value from the object in that order. "hasOwnProperty" is checked also so you definitely have only the object's own properties. Here's an example:
var obj = {"a":1,"b":2,"c":3};
function iterateObjectAlphabetically(obj, callback) {
var arr = [],
i;
for (i in obj) {
if (obj.hasOwnProperty(i)) {
arr.push(i);
}
}
arr.sort();
for (i = 0; i < arr.length; i++) {
var key = obj[arr[i]];
//console.log( obj[arr[i]] ); //here is the sorted value
//do what you want with the object property
if (callback) {
// callback returns arguments for value, key and original object
callback(obj[arr[i]], arr[i], obj);
}
}
}
iterateObjectAlphabetically(obj, function(val, key, obj) {
//do something here
});
Again, this should guarantee that you iterate through in alphabetical order.
Finally, taking it further for the simplest way, this library will recursively allow you to sort any JSON you pass into it: https://www.npmjs.com/package/json-stable-stringify
var stringify = require('json-stable-stringify');
var obj = { c: 8, b: [{z:6,y:5,x:4},7], a: 3 };
console.log(stringify(obj));
Output
{"a":3,"b":[{"x":4,"y":5,"z":6},7],"c":8}
I don't understand why the complexity of the current best answers is needed, to get all the keys recursively. Unless perfect performance is needed, it seems to me that we can just call JSON.stringify() twice, the first time to get all the keys, and the second time, to really do the job. That way, all the recursion complexity is handled by stringify, and we know that it knows its stuff, and how to handle each object type:
function JSONstringifyOrder(obj, space)
{
const allKeys = new Set();
JSON.stringify(obj, (key, value) => (allKeys.add(key), value));
return JSON.stringify(obj, Array.from(allKeys).sort(), space);
}
Or if you want to support older browsers:
function JSONstringifyOrder(obj, space)
{
var allKeys = [];
var seen = {};
JSON.stringify(obj, function (key, value) {
if (!(key in seen)) {
allKeys.push(key);
seen[key] = null;
}
return value;
});
allKeys.sort();
return JSON.stringify(obj, allKeys, space);
}
I think that if you are in control of the JSON generation (and it sounds like you are), then for your purposes this might be a good solution: json-stable-stringify
From the project website:
deterministic JSON.stringify() with custom sorting to get
deterministic hashes from stringified results
If the JSON produced is deterministic you should be able to easily diff/merge it.
You can pass a sorted array of the property names as the second argument of JSON.stringify():
JSON.stringify(obj, Object.keys(obj).sort())
JSON.stringify() replacer function for having object keys sorted in output (supports deeply nested objects).
const replacer = (key, value) =>
value instanceof Object && !(value instanceof Array) ?
Object.keys(value)
.sort()
.reduce((sorted, key) => {
sorted[key] = value[key];
return sorted
}, {}) :
value;
// Usage
// JSON.stringify({c: 1, a: { d: 0, c: 1, e: {a: 0, 1: 4}}}, replacer);
GitHub Gist page here.
Update 2018-7-24:
This version sorts nested objects and supports array as well:
function sortObjByKey(value) {
return (typeof value === 'object') ?
(Array.isArray(value) ?
value.map(sortObjByKey) :
Object.keys(value).sort().reduce(
(o, key) => {
const v = value[key];
o[key] = sortObjByKey(v);
return o;
}, {})
) :
value;
}
function orderedJsonStringify(obj) {
return JSON.stringify(sortObjByKey(obj));
}
Test case:
describe('orderedJsonStringify', () => {
it('make properties in order', () => {
const obj = {
name: 'foo',
arr: [
{ x: 1, y: 2 },
{ y: 4, x: 3 },
],
value: { y: 2, x: 1, },
};
expect(orderedJsonStringify(obj))
.to.equal('{"arr":[{"x":1,"y":2},{"x":3,"y":4}],"name":"foo","value":{"x":1,"y":2}}');
});
it('support array', () => {
const obj = [
{ x: 1, y: 2 },
{ y: 4, x: 3 },
];
expect(orderedJsonStringify(obj))
.to.equal('[{"x":1,"y":2},{"x":3,"y":4}]');
});
});
Deprecated answer:
A concise version in ES2016.
Credit to #codename , from https://stackoverflow.com/a/29622653/94148
function orderedJsonStringify(o) {
return JSON.stringify(Object.keys(o).sort().reduce((r, k) => (r[k] = o[k], r), {}));
}
This is same as Satpal Singh's answer
function stringifyJSON(obj){
keys = [];
if(obj){
for(var key in obj){
keys.push(key);
}
}
keys.sort();
var tObj = {};
var key;
for(var index in keys){
key = keys[index];
tObj[ key ] = obj[ key ];
}
return JSON.stringify(tObj);
}
obj1 = {}; obj1.os="linux"; obj1.name="X";
stringifyJSON(obj1); //returns "{"name":"X","os":"linux"}"
obj2 = {}; obj2.name="X"; obj2.os="linux";
stringifyJSON(obj2); //returns "{"name":"X","os":"linux"}"
A recursive and simplified answer:
function sortObject(obj) {
if(typeof obj !== 'object')
return obj
var temp = {};
var keys = [];
for(var key in obj)
keys.push(key);
keys.sort();
for(var index in keys)
temp[keys[index]] = sortObject(obj[keys[index]]);
return temp;
}
var str = JSON.stringify(sortObject(obj), undefined, 4);
You can sort object by property name in EcmaScript 2015
function sortObjectByPropertyName(obj) {
return Object.keys(obj).sort().reduce((c, d) => (c[d] = obj[d], c), {});
}
You can add a custom toJSON function to your object which you can use to customise the output. Inside the function, adding current properties to a new object in a specific order should preserve that order when stringified.
See here:
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/JSON/stringify
There's no in-built method for controlling ordering because JSON data is meant to be accessed by keys.
Here's a jsfiddle with a small example:
http://jsfiddle.net/Eq2Yw/
Try commenting out the toJSON function - the order of the properties is reversed. Please be aware that this may be browser-specific, i.e. ordering is not officially supported in the specification. It works in the current version of Firefox, but if you want a 100% robust solution, you may have to write your own stringifier function.
Edit:
Also see this SO question regarding stringify's non-deterministic output, especially Daff's details about browser differences:
How to deterministically verify that a JSON object hasn't been modified?
I took the answer from #Jason Parham and made some improvements
function sortObject(obj, arraySorter) {
if(typeof obj !== 'object')
return obj
if (Array.isArray(obj)) {
if (arraySorter) {
obj.sort(arraySorter);
}
for (var i = 0; i < obj.length; i++) {
obj[i] = sortObject(obj[i], arraySorter);
}
return obj;
}
var temp = {};
var keys = [];
for(var key in obj)
keys.push(key);
keys.sort();
for(var index in keys)
temp[keys[index]] = sortObject(obj[keys[index]], arraySorter);
return temp;
}
This fixes the issue of arrays being converted to objects, and it also allows you to define how to sort arrays.
Example:
var data = { content: [{id: 3}, {id: 1}, {id: 2}] };
sortObject(data, (i1, i2) => i1.id - i2.id)
output:
{content:[{id:1},{id:2},{id:3}]}
I just rewrote one of mentioned examples to use it in stringify
const stringifySort = (key, value) => {
if (!value || typeof value !== 'object' || Array.isArray(value)) return value;
return Object.keys(value).sort().reduce((obj, key) => (obj[key]=value[key], obj), {});
};
JSON.stringify({name:"X", os:"linux"}, stringifySort);
The accepted answer does not work for me for nested objects for some reason. This led me to code up my own. As it's late 2019 when I write this, there are a few more options available within the language.
Update: I believe David Furlong's answer is a preferable approach to my earlier attempt, and I have riffed off that. Mine relies on support for Object.entries(...), so no Internet Explorer support.
function normalize(sortingFunction) {
return function(key, value) {
if (typeof value === 'object' && !Array.isArray(value)) {
return Object
.entries(value)
.sort(sortingFunction || undefined)
.reduce((acc, entry) => {
acc[entry[0]] = entry[1];
return acc;
}, {});
}
return value;
}
}
JSON.stringify(obj, normalize(), 2);
--
KEEPING THIS OLDER VERSION FOR HISTORICAL REFERENCE
I found that a simple, flat array of all keys in the object will work. In almost all browsers (not Edge or Internet explorer, predictably) and Node 12+ there is a fairly short solution now that Array.prototype.flatMap(...) is available. (The lodash equivalent would work too.) I have only tested in Safari, Chrome, and Firefox, but I see no reason why it wouldn't work anywhere else that supports flatMap and standard JSON.stringify(...).
function flattenEntries([key, value]) {
return (typeof value !== 'object')
? [ [ key, value ] ]
: [ [ key, value ], ...Object.entries(value).flatMap(flattenEntries) ];
}
function sortedStringify(obj, sorter, indent = 2) {
const allEntries = Object.entries(obj).flatMap(flattenEntries);
const sorted = allEntries.sort(sorter || undefined).map(entry => entry[0]);
return JSON.stringify(obj, sorted, indent);
}
With this, you can stringify with no 3rd-party dependencies and even pass in your own sort algorithm that sorts on the key-value entry pairs, so you can sort by key, payload, or a combination of the two. Works for nested objects, arrays, and any mixture of plain old data types.
const obj = {
"c": {
"z": 4,
"x": 3,
"y": [
2048,
1999,
{
"x": false,
"g": "help",
"f": 5
}
]
},
"a": 2,
"b": 1
};
console.log(sortedStringify(obj, null, 2));
Prints:
{
"a": 2,
"b": 1,
"c": {
"x": 3,
"y": [
2048,
1999,
{
"f": 5,
"g": "help",
"x": false
}
],
"z": 4
}
}
If you must have compatibility with older JavaScript engines, you could use these slightly more verbose versions that emulate flatMap behavior. Client must support at least ES5, so no Internet Explorer 8 or below.
These will return the same result as above.
function flattenEntries([key, value]) {
if (typeof value !== 'object') {
return [ [ key, value ] ];
}
const nestedEntries = Object
.entries(value)
.map(flattenEntries)
.reduce((acc, arr) => acc.concat(arr), []);
nestedEntries.unshift([ key, value ]);
return nestedEntries;
}
function sortedStringify(obj, sorter, indent = 2) {
const sortedKeys = Object
.entries(obj)
.map(flattenEntries)
.reduce((acc, arr) => acc.concat(arr), [])
.sort(sorter || undefined)
.map(entry => entry[0]);
return JSON.stringify(obj, sortedKeys, indent);
}
An additional solution that works for nested objects as well:
const myFunc = (key) =>
JSON.stringify(key, (_, v) =>
v.constructor === Object ? Object.entries(v).sort() : v
);
const jsonFunc = JSON.stringify;
const obj1 = {
key1: "value1",
key2: {
key3: "value2",
key4: "value3",
},
};
const obj2 = {
key2: {
key4: "value3",
key3: "value2",
},
key1: "value1",
};
console.log(`JSON: ${jsonFunc(obj1) === jsonFunc(obj2)}`);
console.log(`My: ${myFunc(obj1) === myFunc(obj2)}`);
Works with lodash, nested objects, any value of object attribute:
function sort(myObj) {
var sortedObj = {};
Object.keys(myObj).sort().forEach(key => {
sortedObj[key] = _.isPlainObject(myObj[key]) ? sort(myObj[key]) : myObj[key]
})
return sortedObj;
}
JSON.stringify(sort(yourObj), null, 2)
It relies on Chrome's and Node's behaviour that the first key assigned to an object is outputted first by JSON.stringify.
After all, it needs an Array that caches all keys in the nested object (otherwise it will omit the uncached keys.) The oldest answer is just plain wrong, because second argument doesn't care about dot-notation. So, the answer (using Set) becomes.
function stableStringify (obj) {
const keys = new Set()
const getAndSortKeys = (a) => {
if (a) {
if (typeof a === 'object' && a.toString() === '[object Object]') {
Object.keys(a).map((k) => {
keys.add(k)
getAndSortKeys(a[k])
})
} else if (Array.isArray(a)) {
a.map((el) => getAndSortKeys(el))
}
}
}
getAndSortKeys(obj)
return JSON.stringify(obj, Array.from(keys).sort())
}
Try:
function obj(){
this.name = '';
this.os = '';
}
a = new obj();
a.name = 'X',
a.os = 'linux';
JSON.stringify(a);
b = new obj();
b.os = 'linux';
b.name = 'X',
JSON.stringify(b);
I made a function to sort object, and with callback .. which actually create a new object
function sortObj( obj , callback ) {
var r = [] ;
for ( var i in obj ){
if ( obj.hasOwnProperty( i ) ) {
r.push( { key: i , value : obj[i] } );
}
}
return r.sort( callback ).reduce( function( obj , n ){
obj[ n.key ] = n.value ;
return obj;
},{});
}
and call it with object .
var obj = {
name : "anu",
os : "windows",
value : 'msio',
};
var result = sortObj( obj , function( a, b ){
return a.key < b.key ;
});
JSON.stringify( result )
which prints {"value":"msio","os":"windows","name":"anu"} , and for sorting with value .
var result = sortObj( obj , function( a, b ){
return a.value < b.value ;
});
JSON.stringify( result )
which prints {"os":"windows","value":"msio","name":"anu"}
If objects in the list does not have same properties, generate a combined master object before stringify:
let arr=[ <object1>, <object2>, ... ]
let o = {}
for ( let i = 0; i < arr.length; i++ ) {
Object.assign( o, arr[i] );
}
JSON.stringify( arr, Object.keys( o ).sort() );
function FlatternInSort( obj ) {
if( typeof obj === 'object' )
{
if( obj.constructor === Object )
{ //here use underscore.js
let PaireStr = _( obj ).chain().pairs().sortBy( p => p[0] ).map( p => p.map( FlatternInSort ).join( ':' )).value().join( ',' );
return '{' + PaireStr + '}';
}
return '[' + obj.map( FlatternInSort ).join( ',' ) + ']';
}
return JSON.stringify( obj );
}
// example as below. in each layer, for objects like {}, flattened in key sort. for arrays, numbers or strings, flattened like/with JSON.stringify.
FlatternInSort( { c:9, b: { y: 4, z: 2, e: 9 }, F:4, a:[{j:8, h:3},{a:3,b:7}] } )
"{"F":4,"a":[{"h":3,"j":8},{"a":3,"b":7}],"b":{"e":9,"y":4,"z":2},"c":9}"
Extending AJP's answer, to handle arrays:
function sort(myObj) {
var sortedObj = {};
Object.keys(myObj).sort().forEach(key => {
sortedObj[key] = _.isPlainObject(myObj[key]) ? sort(myObj[key]) : _.isArray(myObj[key])? myObj[key].map(sort) : myObj[key]
})
return sortedObj;
}
Surprised nobody has mentioned lodash's isEqual function.
Performs a deep comparison between two values to determine if they are
equivalent.
Note: This method supports comparing arrays, array buffers, booleans,
date objects, error objects, maps, numbers, Object objects, regexes,
sets, strings, symbols, and typed arrays. Object objects are compared
by their own, not inherited, enumerable properties. Functions and DOM
nodes are compared by strict equality, i.e. ===.
https://lodash.com/docs/4.17.11#isEqual
With the original problem - keys being inconsistently ordered - it's a great solution - and of course it will just stop if it finds a conflict instead of blindly serializing the whole object.
To avoid importing the whole library you do this:
import { isEqual } from "lodash-es";
Bonus example:
You can also use this with RxJS with this custom operator
export const distinctUntilEqualChanged = <T>(): MonoTypeOperatorFunction<T> =>
pipe(distinctUntilChanged(isEqual));
Here is a clone approach...clone the object before converting to json:
function sort(o: any): any {
if (null === o) return o;
if (undefined === o) return o;
if (typeof o !== "object") return o;
if (Array.isArray(o)) {
return o.map((item) => sort(item));
}
const keys = Object.keys(o).sort();
const result = <any>{};
keys.forEach((k) => (result[k] = sort(o[k])));
return result;
}
If is very new but seems to work on package.json files fine.
Don't be confused with the object monitoring of Chrome debugger. It shows sorted keys in object, even though actually it is not sorted. You have to sort the object before you stringify it.
Before I found libs like fast-json-stable-stringify (haven't tested it in production myself), I was doing it this way:
import { flatten } from "flat";
import { set } from 'lodash/fp';
const sortJson = (jsonString) => {
const object = JSON.parse(jsonString);
const flatObject = flatten(object);
const propsSorted = Object.entries(flatObject).map(([key, value]) => ({ key, value })).sort((a, b) => a.key.localeCompare(b.key));
const objectSorted = propsSorted.reduce((object, { key, value }) => set(key, value, object), {});
return JSON.stringify(objectSorted);
};
const originalJson = JSON.stringify({ c: { z: 3, x: 1, y: 2 }, a: true, b: [ 'a', 'b', 'c' ] });
console.log(sortJson(originalJson)); // {"a":true,"b":["a","b","c"],"c":{"x":1,"y":2,"z":3}}
There is Array.sort method which can be helpful for you. For example:
yourBigArray.sort(function(a,b){
//custom sorting mechanism
});