I have object in this structure:
obj = {
user: { name: 'jeterson' },
title: 'I am a test'
}
I have one key with value: user.name.
I have trying get value like this: obj[key], meaning obj['user.name']. It not works, only works for obj.title.
My object have many values that are also objects, and i want get value like this:
myobject[mykey]
It is possible get value from property object like above ?
You can access it with:
obj['user']['name']
Or alternatively:
obj.user.name
If you want to get from a key like "user.name" to the value, you woulr have to do some logic yourself. You could hack something together like this:
let obj = {
user: {
name: 'jeterson'
},
title: 'I am a test'
}
let key = 'user.name';
let keys = key.split('.');
let res = obj;
while (keys.length > 0 && res) {
let k = keys.shift();
res = res[k];
}
console.log(res) // "jeterson"
When the keys do not match, res holds undefined.
You've got multiple solutions to access an element of an object with its keys:
var obj = {
user: { name: 'jeterson' },
title: 'I am a test'
}
console.log(obj['user']['name']);
console.log(obj['user'].name);
console.log(obj.user['name']);
console.log(obj.user.name);
But you can't do it easily with a variable key = 'user.name'.
If you need to use a variable containing the nested-keys, you could create a function.
Updated answer: An amazingly short way to achieve it is to use .reduce():
// My function
function obj_tree_key(obj, path) {
return path.split('.').reduce((accu, val) => accu[val] || 'Not found', obj);
}
var obj1 = {
user: {
name: 'jeterson'
},
title: 'I am a test'
}
console.log(obj_tree_key(obj1, 'user.name')); // Outputs "jeterson"
// Here is an example with error:
var obj2 = {
user: {
nameeeee: 'jeterson'
},
title: 'I am a test'
}
console.log(obj_tree_key(obj2, 'user.name'));
Old answer: Use a for to loop through the keys and reduce the oject:
// My function
function obj_tree_key(obj, tree_key) {
var result = obj;
var keys = tree_key.split('.');
for (var i = 0; i < keys.length; i++) {
result = result[keys[i]] || 'Not found'; // Error handling
}
return result;
}
var obj1 = {
user: {
name: 'jeterson'
},
title: 'I am a test'
}
console.log(obj_tree_key(obj1, 'user.name')); // Outputs "jeterson"
// Here is an example with error:
var obj2 = {
user: {
nameeeee: 'jeterson'
},
title: 'I am a test'
}
console.log(obj_tree_key(obj2, 'user.name'));
Hope it helps.
first get the user, then the name:
obj['user']['name']
or
obj.user.name
You can also use
obj.user.name
You could access it using
console.log(obj.user.name);
You can do it in 2 way:
obj['user']['name']
or
obj.user.name
Related
I have a set of object of object. For example
{
"123":{
id:123,
name:"abc"
},
"456":{
id:456,
name:"def"
},
"789":{
id:789,
name:"ghi"
}
}
I would like to know how to loop over my object and check if the value "def" exist in the object list?
Can I know how to loop through every iteration and only do decision ?? For example first iteration is abc then next is def then next is ghi . because abc and def is not same but when come to def and def it is same .Can I do action or logic after finish loop through every iteration ?
Use a for loop on the object to check that value exist in name property or not:
var obj = {
123: {
id: 123,
name: 'abc'
},
456: {
id: 456,
name: 'def'
},
789: {
id: 789,
name: 'ghi'
}
};
var checkVal = 'def';
let match = false;
for(var objKey in obj) {
if(obj[objKey].name === checkVal) {
match = true;
}
}
console.log('found ', match);
There are a couple of ways to loop through an object in Javascript, depending on what version you are using.
The basics of it Ankit talked about in his answer:
const search = {
"123":{
id:123,
name:"abc"
},
"456":{
id:456,
name:"def"
},
"789":{
id:789,
name:"ghi"
}
};
for(let key in search) {
if(search[key].name == 'def') {
console.log(search[key]);
}
}
If you are using a newer version of Javascript, you can do the following:
const search = {
"123":{
id:123,
name:"abc"
},
"456":{
id:456,
name:"def"
},
"789":{
id:789,
name:"ghi"
}
}
for(let obj of Object.values(search)){
if(obj.name==='def') console.log(obj);
}
// or, very similarly
for(let key of Object.keys(search)) {
let obj = search[key];
if(obj.name=='def') console.log(obj);
}
Or, lastly.
const search = {
"123":{
id:123,
name:"abc"
},
"456":{
id:456,
name:"def"
},
"789":{
id:789,
name:"ghi"
}
}
for(let [key, obj] of Object.entries(search)){
if(obj.name=='def') console.log('found on key ', key, 'value:', obj);
}
Note that the last one uses the destructuring assignment so that you do not need to use a placeholder variable simply to assign key and object/value out inside the loop.
This is an object to be processed:
var q = {
email: {contains: "noname#hotmail.com"},
name: {contains: "someuser"}
};
I would like to go through each key of q and if the corresponding value is an object that has the property contains then replace it with $regex.
Related information can be found here: JavaScript: Object Rename Key
You can try the following way:
var q = {
email: {contains: "noname#hotmail.com"},
name: {contains: "someuser"}
};
for(var k in q){
if(q[k].hasOwnProperty('contains')){
Object.defineProperty(q[k], '$regex',
Object.getOwnPropertyDescriptor(q[k], 'contains'));
delete q[k]['contains'];
}
}
console.log(q);
for(const obj of Object.values(q)) {
obj.$regex = obj.contains;
delete obj.contains;
}
Just go over all values inside q and copy the contains property into the $regex property.
To iterate over object keys first you have to fetch them, here is one simple approach
const keys = Object.keys(q); // ["email", "name"]
Now iterate over the array which we got and perform regex testing;
keys.forEach(key => {
let value = q[key].contains;
// create $regex and assign value
// remove .contains
})
You can loop through the objects and first put current value of contains property in $regex and then delete the contains property.
Below is working code:
var q = {
email: {
contains: "noname#hotmail.com"
},
name: {
contains: "someuser"
}
};
for (var i of Object.values(q)) {
if (i.hasOwnProperty("contains")) {
i.$regex = i.contains;
delete i.contains;
}
}
console.log(q);
var q = {
email: {contains: "noname#hotmail.com"},
name: {contains: "someuser"}
};
Object.keys(q).forEach(k => {
if (typeof q[k].contains != 'undefined'){
q[k].$regex = q[k].contains;
delete q[k].contains;
}
})
console.log(q);
Other version using Es 6 features
const renameProp = (
oldProp,
newProp,
{ [oldProp]: old, ...others }
) => {
return {
[newProp]: old,
...others
};
};
let q = {
email: {contains: "noname#hotmail.com"},
name: {contains: "someuser"}
};
let newObj = {}
for (let propName in q) {
newObj[propName] = renameProp("contains","$regex",q[propName])
}
console.log(newObj)
var q = {
email: {
contains: "noname#hotmail.com"
},
name: {
contains: "someuser"
},
asdf: "asdf"
};
Object.keys(q).forEach(function(item, index) {
if (typeof q[item] == "object" && q[item].contains) {
q[item].$regex = q[item].contains;
delete q[item].contains;
}
})
At present, I do this approach:
var obj = {
sender: {
name: "tech"
}
}
var str = "sender.name".split('.');
console.log( obj[str[0]][str[1]] ); //getting update as 'Tech'
In the above I use obj[str[0]][str[1]] for just 2 step, this is works fine. In case if I received a long node parent and child this approach not going to work.
Instead is there any correct dynamic way to do this?
You can use array#reduce to navigate through each key.
var obj = { sender: { name: "tech" } };
var str = "sender.name".split('.').reduce((r,k) => r[k],obj);
console.log(str);
You can use reduce:
var obj = {
foo: {
bar: {
baz: {
sender: {
name: "tech"
}
}
}
}
}
const props = "foo.bar.baz.sender.name".split('.');
const val = props.reduce((currObj, prop) => currObj[prop], obj);
console.log(val);
You could split the string and reduce the path for the result. The function uses a default object for missing or not given properties.
function getValue(object, path) {
return path
.split('.')
.reduce(function (o, k) { return (o || {})[k]; }, object);
}
var obj = { sender: { name: "tech" } },
str = "sender.name";
console.log(getValue(obj, str));
You should be looking into libraries such as "https://lodash.com/"
https://lodash.com/docs/4.17.10
Use _.get : https://lodash.com/docs/4.17.10#get
You can simply write _.get(obj, 'sender.name', 'default') and you will get the value as you expect
I need to destructure a nested object. what is the best way to avoid exceptions when some of the nested properties are missing, while assigning those who do exist?
const data = {
title: 'hello',
// nest: {
// road: 5
// }
};
const { title, nest: { road = '' } } = data;
console.log(road);
/** i want it to return '' or undefined.
* actually it returns: Cannot match against 'undefined' or 'null'
*
*/
console.log(title)
/** i want it to return 'hello'
* actually: never got there as there was an exception.
*/
You can assign in a parent object level to empty object (or with value) even if it has further nested object destruction:
const { title, nest: { road = '<default road>' } = {} } = data;
const data = {
title: 'hello',
//nest: {
// road: 5
//}
};
const { title, nest: { road = '<default road>' } = {} } = data;
console.log(title);
console.log(road);
And also, you are doing it wrong, if you are destructing using
{title: englishTitle} = {title: 1234}
then, you should use englishTitle to get the value 1234, and not title, or use
{title} = {title: 1234}
and use title to get 1234
I have an array of objects that can be of any length and any depth. I need to be able to find an object by its id and then modify that object within the array. Is there an efficient way to do this with either lodash or pure js?
I thought I could create an array of indexes that led to the object but constructing the expression to access the object with these indexes seems overly complex / unnecessary
edit1; thanks for all yours replies I will try and be more specific. i am currently finding the location of the object I am trying to modify like so. parents is an array of ids for each parent the target object has. ancestors might be a better name for this array. costCenters is the array of objects that contains the object I want to modify. this function recurses and returns an array of indexes that lead to the object I want to modify
var findAncestorsIdxs = function(parents, costCenters, startingIdx, parentsIdxs) {
var idx = startingIdx ? startingIdx : 0;
var pidx = parentsIdxs ? parentsIdxs : [];
_.each(costCenters, function(cc, ccIdx) {
if(cc.id === parents[idx]) {
console.log(pidx);
idx = idx + 1;
pidx.push(ccIdx);
console.log(pidx);
pidx = findAncestorsIdx(parents, costCenters[ccIdx].children, idx, pidx);
}
});
return pidx;
};
Now with this array of indexes how do I target and modify the exact object I want? I have tried this where ancestors is the array of indexes, costCenters is the array with the object to be modified and parent is the new value to be assigned to the target object
var setParentThroughAncestors = function(ancestors, costCenters, parent) {
var ccs = costCenters;
var depth = ancestors.length;
var ancestor = costCenters[ancestors[0]];
for(i = 1; i < depth; i++) {
ancestor = ancestor.children[ancestors[i]];
}
ancestor = parent;
console.log(ccs);
return ccs;
};
this is obviously just returning the unmodified costCenters array so the only other way I can see to target that object is to construct the expression like myObjects[idx1].children[2].grandchildren[3].ggranchildren[4].something = newValue. is that the only way? if so what is the best way to do that?
You can use JSON.stringify for this. It provides a callback for each visited key/value pair (at any depth), with the ability to skip or replace.
The function below returns a function which searches for objects with the specified ID and invokes the specified transform callback on them:
function scan(id, transform) {
return function(obj) {
return JSON.parse(JSON.stringify(obj, function(key, value) {
if (typeof value === 'object' && value !== null && value.id === id) {
return transform(value);
} else {
return value;
}
}));
}
If as the problem is stated, you have an array of objects, and a parallel array of ids in each object whose containing objects are to be modified, and an array of transformation functions, then it's just a matter of wrapping the above as
for (i = 0; i < objects.length; i++) {
scan(ids[i], transforms[i])(objects[i]);
}
Due to restrictions on JSON.stringify, this approach will fail if there are circular references in the object, and omit functions, regexps, and symbol-keyed properties if you care.
See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_native_JSON#The_replacer_parameter for more info.
As Felix Kling said, you can iterate recursively over all objects.
// Overly-complex array
var myArray = {
keyOne: {},
keyTwo: {
myId: {a: '3'}
}
};
var searchId = 'myId', // Your search key
foundValue, // Populated with the searched object
found = false; // Internal flag for iterate()
// Recursive function searching through array
function iterate(haystack) {
if (typeof haystack !== 'object' || haystack === null) return; // type-safety
if (typeof haystack[searchId] !== 'undefined') {
found = true;
foundValue = haystack[searchId];
return;
} else {
for (var i in haystack) {
// avoid circular reference infinite loop & skip inherited properties
if (haystack===haystack[i] || !haystack.hasOwnProperty(i)) continue;
iterate(haystack[i]);
if (found === true) return;
}
}
}
// USAGE / RESULT
iterate(myArray);
console.log(foundValue); // {a: '3'}
foundValue.b = 4; // Updating foundValue also updates myArray
console.log(myArray.keyTwo.myId); // {a: '3', b: 4}
All JS object assignations are passed as reference in JS. See this for a complete tutorial on objects :)
Edit: Thanks #torazaburo for suggestions for a better code.
If each object has property with the same name that stores other nested objects, you can use: https://github.com/dominik791/obj-traverse
findAndModifyFirst() method should solve your problem. The first parameter is a root object, not array, so you should create it at first:
var rootObj = {
name: 'rootObject',
children: [
{
'name': 'child1',
children: [ ... ]
},
{
'name': 'child2',
children: [ ... ]
}
]
};
Then use findAndModifyFirst() method:
findAndModifyFirst(rootObj, 'children', { id: 1 }, replacementObject)
replacementObject is whatever object that should replace the object that has id equal to 1.
You can try it using demo app:
https://dominik791.github.io/obj-traverse-demo/
Here's an example that extensively uses lodash. It enables you to transform a deeply nested value based on its key or its value.
const _ = require("lodash")
const flattenKeys = (obj, path = []) => (!_.isObject(obj) ? { [path.join('.')]: obj } : _.reduce(obj, (cum, next, key) => _.merge(cum, flattenKeys(next, [...path, key])), {}));
const registrations = [{
key: "123",
responses:
{
category: 'first',
},
}]
function jsonTransform (json, conditionFn, modifyFn) {
// transform { responses: { category: 'first' } } to { 'responses.category': 'first' }
const flattenedKeys = Object.keys(flattenKeys(json));
// Easily iterate over the flat json
for(let i = 0; i < flattenedKeys.length; i++) {
const key = flattenedKeys[i];
const value = _.get(json, key)
// Did the condition match the one we passed?
if(conditionFn(key, value)) {
// Replace the value to the new one
_.set(json, key, modifyFn(key, value))
}
}
return json
}
// Let's transform all 'first' values to 'FIRST'
const modifiedCategory = jsonTransform(registrations, (key, value) => value === "first", (key, value) => value = value.toUpperCase())
console.log('modifiedCategory --', modifiedCategory)
// Outputs: modifiedCategory -- [ { key: '123', responses: { category: 'FIRST' } } ]
I needed to modify deeply nested objects too, and found no acceptable tool for that purpose. Then I've made this and pushed it to npm.
https://www.npmjs.com/package/find-and
This small [TypeScript-friendly] lib can help with modifying nested objects in a lodash manner. E.g.,
var findAnd = require("find-and");
const data = {
name: 'One',
description: 'Description',
children: [
{
id: 1,
name: 'Two',
},
{
id: 2,
name: 'Three',
},
],
};
findAnd.changeProps(data, { id: 2 }, { name: 'Foo' });
outputs
{
name: 'One',
description: 'Description',
children: [
{
id: 1,
name: 'Two',
},
{
id: 2,
name: 'Foo',
},
],
}
https://runkit.com/embed/bn2hpyfex60e
Hope this could help someone else.
I wrote this code recently to do exactly this, as my backend is rails and wants keys like:
first_name
and my front end is react, so keys are like:
firstName
And these keys are almost always deeply nested:
user: {
firstName: "Bob",
lastName: "Smith",
email: "bob#email.com"
}
Becomes:
user: {
first_name: "Bob",
last_name: "Smith",
email: "bob#email.com"
}
Here is the code
function snakeCase(camelCase) {
return camelCase.replace(/([A-Z])/g, "_$1").toLowerCase()
}
export function snakeCasedObj(obj) {
return Object.keys(obj).reduce(
(acc, key) => ({
...acc,
[snakeCase(key)]: typeof obj[key] === "object" ? snakeCasedObj(obj[key]) : obj[key],
}), {},
);
}
Feel free to change the transform to whatever makes sense for you!