I'm pulling items out of the DOM with jQuery and want to set a property on an object using the id of the DOM element.


const obj = {}

jQuery(itemsFromDom).each(function() {
  const element = jQuery(this)
  const name = element.attr('id')
  const value = element.attr('value')

  // Here is the problem
  obj.name = value

If itemsFromDom includes an element with an id of "myId", I want obj to have a property named "myId". The above gives me name.

How do I name a property of an object using a variable using JavaScript?

Solution 1

You can use this equivalent syntax:

obj[name] = value


let obj = {};
obj["the_key"] = "the_value";

or with ES6 features:

let key = "the_key";
let obj = {
  [key]: "the_value",

in both examples, console.log(obj) will return: { the_key: 'the_value' }

Solution 2

With ECMAScript 2015 you can do it directly in object declaration using bracket notation:

var obj = {
  [key]: value

Where key can be any sort of expression (e.g. a variable) returning a value:

var obj = {
  ['hello']: 'World',
  [x + 2]: 42,
  [someObject.getId()]: someVar

Solution 3

You can even make List of objects like this

var feeTypeList = [];
$('#feeTypeTable > tbody > tr').each(function (i, el) {
    var feeType = {};

    var $ID = $(this).find("input[id^=txtFeeType]").attr('id');

    feeType["feeTypeID"] = $('#ddlTerm').val();
    feeType["feeTypeName"] = $('#ddlProgram').val();
    feeType["feeTypeDescription"] = $('#ddlBatch').val();


Solution 4

There are two different notations to access object properties

  • Dot notation: myObj.prop1
  • Bracket notation: myObj["prop1"]

Dot notation is fast and easy but you must use the actual property name explicitly. No substitution, variables, etc.

Bracket notation is open ended. It uses a string but you can produce the string using any legal js code. You may specify the string as literal (though in this case dot notation would read easier) or use a variable or calculate in some way.

So, these all set the myObj property named prop1 to the value Hello:

// quick easy-on-the-eye dot notation
myObj.prop1 = "Hello";

// brackets+literal
myObj["prop1"] = "Hello";

// using a variable
var x = "prop1"; 
myObj[x] = "Hello";                     

// calculate the accessor string in some weird way
var numList = [0,1,2];
myObj[ "prop" + numList[1] ] = "Hello";     


myObj.[xxxx] = "Hello";      // wrong: mixed notations, syntax fail
myObj[prop1] = "Hello";      // wrong: this expects a variable called prop1

tl;dnr: If you want to compute or reference the key you must use bracket notation. If you are using the key explicitly, then use dot notation for simple clear code.

Note: there are some other good and correct answers but I personally found them a bit brief coming from a low familiarity with JS on-the-fly quirkiness. This might be useful to some people.

Solution 5

With lodash, you can create new object like this _.set:

obj = _.set({}, key, val);

Or you can set to existing object like this:

var existingObj = { a: 1 };
_.set(existingObj, 'a', 5); // existingObj will be: { a: 5 }

You should take care if you want to use dot (".") in your path, because lodash can set hierarchy, for example:

_.set({}, "a.b.c", "d"); // { "a": { "b": { "c": "d" } } }

Solution 6

First we need to define key as variable and then we need to assign as key as object., for example

var data = {key:'dynamic_key',value:'dynamic_value'}
var key = data.key;
var obj = { [key]: data.value}

Solution 7

Related to the subject, not specifically for jquery though. I used this in ec6 react projects, maybe helps someone:

this.setState({ [`${name}`]: value}, () => {
      console.log("State updated: ", JSON.stringify(this.state[name]));

PS: Please mind the quote character.

Solution 8

With the advent of ES2015 Object.assign and computed property names the OP's code boils down to:

var obj = Object.assign.apply({}, $(itemsFromDom).map((i, el) => ({[el.id]: el.value})));

Solution 9

ajavascript have two type of annotation for fetching javascript Object properties:

Obj = {};

1) (.) annotation eg. Obj.id this will only work if the object already have a property with name 'id'

2) ([]) annotation eg . Obj[id] here if the object does not have any property with name 'id',it will create a new property with name 'id'.

so for below example:

A new property will be created always when you write Obj[name]. And if the property already exist with the same name it will override it.

const obj = {}
    jQuery(itemsFromDom).each(function() {
      const element = jQuery(this)
      const name = element.attr('id')
      const value = element.attr('value')
      // This will work
      obj[name]= value;

Solution 10

If you want to add fields to an object dynamically, simplest way to do it is as follows:

let params = [
  { key: "k1", value: 1 },
  { key: "k2", value: 2 },
  { key: "k3", value: 3 },
let data = {};

for (let i = 0; i < params.length; i++) {
  data[params[i].key] = params[i].value;

console.log(data); // -> { k1: 1, k2: 2, k3: 3 }

Solution 11

The 3 ways to access the object value We can output the object value by passing in the appropriate key. Because I used emoji as the key in my example, it's a bit tricky. So let's look at a easier example.

let me = {
  name: 'samantha',

// 1. Dot notation
me.name; // samantha

// 2. Bracket notation (string key)
me['name']; // samantha

// 3. Bracket notation (variable key)
let key = 'name';
me[key]; // samantha

know more

Solution 12

If you have object, you can make array of keys, than map through, and create new object from previous object keys, and values.

.map(el =>{
 const obj = {};

Solution 13

objectname.newProperty = value;

Solution 14

const data = [{
    name: 'BMW',
    value: '25641'
  }, {
    name: 'Apple',
    value: '45876'
    name: 'Benz',
    value: '65784'
    name: 'Toyota',
    value: '254'

const obj = {
  carsList: [{
    name: 'Ford',
    value: '47563'
  }, {
    name: 'Toyota',
    value: '254'
  pastriesList: [],
  fruitsList: [{
    name: 'Apple',
    value: '45876'
  }, {
    name: 'Pineapple',
    value: '84523'

let keys = Object.keys(obj);

result = {};

for(key of keys){
    let a =  [...data,...obj[key]];
    result[key] = a;