Pluck an object's properties and values into a new object

Question

I want a nice small one liner to use an array, for example ['postcode','town'] , and then pluck just these properties from a larger object.

So this:

const fields = ['postcode','town'];
const obj = {
    name: 'test',
    postcode: 'SS2 5JJ',
    town: 'Somewhere',
    other: 'info'
}

Would become this:

const filtered = {
    postcode: 'SS2 5JJ',
    town: 'Somewhere',
}

I did find this however I have mis-understood it I believe:

const fields = ['postcode','town'];
Object.keys(fields).map(e => fields[e])

What is the best way to do this?

Answer 1

You could use Array.reduce

 const fields = ['postcode', 'town']; const obj = { name: 'test', postcode: 'SS2 5JJ', town: 'Somewhere', other: 'info' }; const filteredObj = fields.reduce((acc, cur) => Object.assign(acc, { [cur]: obj[cur] }), {}); console.log(filteredObj);

Answer 2

Maybe:

let res = Object.fromEntries(Object.entries(obj).filter(e => fields.includes(e[0]))

Answer 3

You can map your array fields to [key, value] which will create an array of [key, value] pairs. Once you have this array, you can use Object.fromEntries() to build your object for each key-value pair:

 const fields = ['postcode','town']; const obj = { name: 'test', postcode: 'SS2 5JJ', town: 'Somewhere', other: 'info' }; const res = Object.fromEntries(fields.map(key => [key, obj[key]])); console.log(res);

Answer 4

"Best" is of course a subjective concept. But I think that the reduce function is the cleanest way of doing it. That way there is no need to chain together different functions.

const filtered = fields.reduce((prev, key) => ({[key]: obj[key], ...prev}), {});

Answer 5

 const fields = ['postcode','town']; const obj = { name: 'test', postcode: 'SS2 5JJ', town: 'Somewhere', other: 'info' } const newObj = {}; Object.keys(obj).forEach(key => { if (fields.includes(key)) { newObj[key] = obj[key]; } }); console.log(newObj);