Return an array of a single property from an array of objects in Javascript

Question

I'm looking for an way to return an array of only a single property of an array of objects in Javascript. Specifically, if I have an array structure formatted to the following specification:

[
    { prop1: "someVar", prop2: "anotherVar" }, 
    { prop1: "foo", prop2: "bar" }, 
    { prop1: "abc", prop2: "def" }
]

How can I return an array of just the prop1 properties? Like following:

[ "someVar", "foo", "abc" ]

I thought I could simply use the .filter method on my original array, like so:

self.myArray.filter(function (el) {
        return el.prop1;
    });

But that clearly doesn't work... Ideas?

Renato Gama · Accepted Answer · 2014-12-05 01:12:35Z

7

Try this;

var newArray = [
    { prop1: "someVar", prop2: "anotherVar" }, 
    { prop1: "foo", prop2: "bar" }, 
    { prop1: "abc", prop2: "def" }
].map(function(item) {
    return item.prop1;
});

In case prop1 is dynamic then you can have a function like;

function extractProperty(array, prop) { //you may want to give it a better name
    return array.map(function(item) {
        return item[prop]; 
    });
}

You can use it like;

var array = extractProperty([
    { prop1: "someVar", prop2: "anotherVar" }, 
    { prop1: "foo", prop2: "bar" }, 
    { prop1: "abc", prop2: "def" }
], 'prop1');

answered Dec 5, 2014 at 1:12

Renato Gama

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6 Comments

Madbreaks Over a year ago

Gotta think op wants "prop1" (e.g. which property) to be dynamic

Madbreaks Over a year ago

Yep - exactly. I deleted my answer that was the same, nice answer. +1

Ray Toal Over a year ago

The formal computer-sciencey data-sciency name for it would be project, in case anyone cares.

marked-down Over a year ago

@renatoargh, thanks for the solution. Yep, the property in question is not dynamic but it's nice to know what would be needed in case it was dynamic. Cheers.

Ray Toal Over a year ago

Also, when you ever get into cool libraries, like underscore.js, you can just use pluck which is already in the library for you.

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