From an array of objects, extract value of a property as array

Question

I have JavaScript object array with the following structure:

objArray = [ { foo: 1, bar: 2}, { foo: 3, bar: 4}, { foo: 5, bar: 6} ]; 

I want to extract a field from each object, and get an array containing the values, for example field foo would give array [ 1, 3, 5 ].

I can do this with this trivial approach:

function getFields(input, field) {     var output = [];     for (var i=0; i < input.length ; ++i)         output.push(input[i][field]);     return output; }  var result = getFields(objArray, "foo"); // returns [ 1, 3, 5 ] 

Is there a more elegant or idiomatic way to do this, so that a custom utility function would be unnecessary?

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Note about suggested duplicate, it covers how to convert a single object to an array.

Answer 1

Here is a shorter way of achieving it:

let result = objArray.map(a => a.foo); 

OR

let result = objArray.map(({ foo }) => foo) 

You can also check Array.prototype.map().

Answer 2

Yes, but it relies on an ES5 feature of JavaScript. This means it will not work in IE8 or older.

var result = objArray.map(function(a) {return a.foo;}); 

On ES6 compatible JS interpreters you can use an arrow function for brevity:

var result = objArray.map(a => a.foo); 

Array.prototype.map documentation