Add key value pair to all objects in array

Question

I wanted to add a key:value parameter to all the objects in an array.

eg:

var arrOfObj = [{name: 'eve'},{name:'john'},{name:'jane'}];

Now I wanted to add a new parameter, isActive to all the objects so the resulting array will look like.

eg:

    [{
    name: 'eve',
    isActive: true
}, {
    name: 'john',
    isActive: true
}, {
    name: 'jane',
    isActive: true
}]

I can always loop through the array and insert a key,value pair. But was wondering if there was a better way to do so

Answer 1

You can do this with map()

var arrOfObj = [{
  name: 'eve'
}, {
  name: 'john'
}, {
  name: 'jane'
}];

var result = arrOfObj.map(function(o) {
  o.isActive = true;
  return o;
})

console.log(result)

If you want to keep original array you can clone objects with Object.assign()

var arrOfObj = [{
  name: 'eve'
}, {
  name: 'john'
}, {
  name: 'jane'
}];

var result = arrOfObj.map(function(el) {
  var o = Object.assign({}, el);
  o.isActive = true;
  return o;
})

console.log(arrOfObj);
console.log(result);

Answer 2

I would be a little cautious with some of the answers presented in here, the following examples outputs differently according with the approach:

const list = [ { a : 'a', b : 'b' } , { a : 'a2' , b : 'b2' }]

console.log(list.map(item => item.c = 'c'))
// [ 'c', 'c' ]

console.log(list.map(item => {item.c = 'c'; return item;}))
// [ { a: 'a', b: 'b', c: 'c' }, { a: 'a2', b: 'b2', c: 'c' } ]

console.log(list.map(item => Object.assign({}, item, { c : 'c'})))
// [ { a: 'a', b: 'b', c: 'c' }, { a: 'a2', b: 'b2', c: 'c' } ]

I have used node v8.10.0 to test the above pieces of code.

Answer 3

You may also try this:

arrOfObj.forEach(function(item){item.isActive = true;});

console.log(arrOfObj);

Answer 4

@Redu's solution is a good solution

arrOfObj.map(o => o.isActive = true;) but Array.map still counts as looping through all items.

if you absolutely don't want to have any looping here's a dirty hack :

Object.defineProperty(Object.prototype, "isActive",{
  value: true,
  writable: true,
  configurable: true,
  enumerable: true
});

my advice is not to use it carefully though, it will patch absolutely all javascript Objects (Date, Array, Number, String or any other that inherit Object ) which is really bad practice...

Answer 5

arrOfObj.map(o => { 
  o.isActive = true; 
  return o; 
});

Answer 6

_.forEach(arrOfObj,(arrVal,arrIn) => {
             arrVal.isAcitve = true;
            }

Answer 7

var arrOfObj = [{name: 'eve'},{name:'john'},{name:'jane'}];
const result = arrOfObj.map((name) => {
    name["isActive"] = true;
    return name;
});
console.log(result);

Answer 8

Looping through the array and inserting a key, value pair is about your best solution. You could use the 'map' function but it is just a matter of preference.

var arrOfObj = [{name: 'eve'},{name:'john'},{name:'jane'}];
arrOfObj.map(function (obj) { 
   obj.isActive = true;
});

Answer 9

Simply use map function:

var arrOfObj = arrOfObj.map(function(element){
   element.active = true;
   return element;
}

Map is pretty decent on compatibility: you can be reasonably safe from IE <= 9.

However, if you are 100% sure your users will use ES6 Compatible browser, you can shorten that function with arrow functions, as @Sergey Panfilov has suggested.

Answer 10

    var arrOfObj = [{name: 'eve'},{name:'john'},{name:'jane'}];
    var injectObj = {isActive:true, timestamp:new Date()};

    // function to inject key values in all object of json array

    function injectKeyValueInArray (array, keyValues){
        return new Promise((resolve, reject) => {
            if (!array.length)
                return resolve(array);

            array.forEach((object) => {
                for (let key in keyValues) {
                    object[key] = keyValues[key]
                }
            });
            resolve(array);
        })
    };

//call function to inject json key value in all array object
    injectKeyValueInArray(arrOfObj,injectObj).then((newArrOfObj)=>{
        console.log(newArrOfObj);
    });

Output like this:-

[ { name: 'eve',
    isActive: true,
    timestamp: 2017-12-16T16:03:53.083Z },
  { name: 'john',
    isActive: true,
    timestamp: 2017-12-16T16:03:53.083Z },
  { name: 'jane',
    isActive: true,
    timestamp: 2017-12-16T16:03:53.083Z } ]

Answer 11

let arrOfObj = [{name: 'eve'},{name:'john'},{name:'jane'}];
let newArr = arrOfObj.map(i => ({...i,isActive: true}));

Here what i did was i spread the current object and insert a new key with a value to the object and return it as a new object.