Take the property values of objects within an array out of the objects in an efficient way

Question

I have an array with objects returned by a server like this:

myArr = [{
    "id": 1
}, {
    "id": 2
}, {
    "id": 3
}, {
    "id": 4
}, {
    "id": 5
}, {
     "id": 6
}, {
    "id": 7
}, {
    "id": 8
}, {
    "id": 9
}, {
    "id": 10
}];

I need this to become:

myArr = [
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10
];

I can loop through the array of course, something like:

// array to hold property values
let myNewArr = [];

// loop through the objects and take the value of id of each object
for (let i = 0; i < myArr.length; ++i) {
    myNewArr.push(myArr[i].id);
}

Is there a more efficient way to do this, preferably using Lodash? I don't want to add another loop to the code, as it's already riddled with loops.

Luca De Nardi · Accepted Answer · 2017-10-31 10:59:47Z

4

Array map is what you're looking for:

myArr.map(function(x){ return x.id; })

It automatically cycles your array and "extract" the id value of your inner objects, returning an array.

answered Oct 31, 2017 at 10:59

Luca De Nardi

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1 Comment

erol_smsr Over a year ago

Thanks! I accepted Hussain's answer, though, because he used Lodash (it allows my code to be more similar to the rest of the code I'm working on).

Hussain Ali Akbar · Accepted Answer · 2017-10-31 11:04:36Z

1

with lodash:

let myArr = _.map(myArr, (b) => b.id);

with arrow operator:

let d = myArr.map(b => b.id);

answered Oct 31, 2017 at 11:04

Hussain Ali Akbar

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1 Comment

erol_smsr Over a year ago

Thanks this is perfect :)

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