How to get a subset of a javascript object's properties

Question

Say I have an object:

elmo = { 
  color: \'red\',
  annoying: true,
  height: \'unknown\',
  meta: { one: \'1\', two: \'2\'}
};

I want to m

Answer 1

Destructuring assignment with dynamic properties

This solution not only applies to your specific example but is more generally applicable:

const subset2 = (x, y) => ({[x]:a, [y]:b}) => ({[x]:a, [y]:b});

const subset3 = (x, y, z) => ({[x]:a, [y]:b, [z]:c}) => ({[x]:a, [y]:b, [z]:c});

// const subset4...etc.


const o = {a:1, b:2, c:3, d:4, e:5};


const pickBD = subset2("b", "d");
const pickACE = subset3("a", "c", "e");


console.log(
  pickBD(o), // {b:2, d:4}
  pickACE(o) // {a:1, c:3, e:5}
);

You can easily define subset4 etc. to take more properties into account.

Answer 2

I suggest taking a look at Lodash; it has a lot of great utility functions.

For example pick() would be exactly what you seek:

var subset = _.pick(elmo, ['color', 'height']);

fiddle

Answer 3

One more solution:

var subset = {
   color: elmo.color,
   height: elmo.height 
}

This looks far more readable to me than pretty much any answer so far, but maybe that's just me!

Answer 4

This works for me in Chrome console. Any problem with this?

var { color, height } = elmo
var subelmo = { color, height }
console.log(subelmo) // {color: "red", height: "unknown"}

Answer 5

I am adding this answer because none of the answer used Comma operator.

It's very easy with destructuring assignment and , operator

const object = { a: 5, b: 6, c: 7  };
const picked = ({a,c} = object, {a,c})

console.log(picked);

Answer 6

How about:

function sliceObj(obj) {
  var o = {}
    , keys = [].slice.call(arguments, 1);
  for (var i=0; i<keys.length; i++) {
    if (keys[i] in obj) o[keys[i]] = obj[keys[i]];
  }
  return o;
}

var subset = sliceObj(elmo, 'color', 'height');