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 into dynamically named variables is impossible in JavaScript as discussed in this question.

To set keys dynamically, you can use reduce function without mutating object as follows:

const getSubset = (obj, ...keys) => keys.reduce((a, c) => ({ ...a, [c]: obj[c] }), {});

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

const subset = getSubset(elmo, 'color', 'annoying')
console.log(subset)

Should note that you're creating a new object on every iteration though instead of updating a single clone. – mpen

below is a version using reduce with single clone (updating initial value passed in to reduce).

const getSubset = (obj, ...keys) => keys.reduce((acc, curr) => {
  acc[curr] = obj[curr]
  return acc
}, {})

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

const subset = getSubset(elmo, 'annoying', 'height', 'meta')
console.log(subset)