Javascript Array, return key:value pairs with specific key

Question

Problem I have a Javascript array and I'm trying to return only the key:value pairs that match a specific key in the most efficient way possible.

I've tried using a Foreach loop and pushing each key:value to a new array but that seems like an inefficient way to do it and overly complex.

Code

initialArray = [ { friends: [],
    otherFriends: [],
    _id: 5c6c7132f9bf4bdab9c906ff,
    user: 5c65d9438e4a834c8e85dd7d,
    password: '$2b$10$LMFB6CBdwxSAfjog/Uo3t.u/G0GBtzfJnYdpvlrSNchA9.jlNOdAa',
    email: 'sparky2df3dfdfdf2@gmail.com',
    createdAt: 2019-02-19T21:12:18.569Z,
    updatedAt: null,
    online: false,
    __v: 0 },
  { friends: [],
    otherFriends: [],
    _id: 5c6ccd6d3a0dc4e4951c2bee,
    user: 5c65d9438e4a834c8e85dd7e,
    password: '$2b$10$gEAbOAdKyHJfAksr5txUNOudCautRs1w/pubplQKzZ5PefhfOOEhq',
    email: 'fdagssd@gmail.com',
    createdAt: 2019-02-20T03:45:49.703Z,
    updatedAt: null,
    online: false,
    __v: 0 } ] 

Desired Array

[ 
    { user: 5c65d9438e4a834c8e85dd7d },
    { user: 5c65d9438e4a834c8e85dd7e }
] 

Current Method

const newArray = []
initialArray.forEach(element => {
            newArray.push({key: element.user});
        });

If anyone has any suggestions that would be amazing! Thanks in advance :)

Answer 1

You could use a destructuring assignment for user and map this short hand property .

 var initialArray = [{ friends: [], otherFriends: [], _id: '5c6c7132f9bf4bdab9c906ff', user: '5c65d9438e4a834c8e85dd7d', password: '$2b$10$LMFB6CBdwxSAfjog/Uo3t.u/G0GBtzfJnYdpvlrSNchA9.jlNOdAa', email: 'sparky2df3dfdfdf2@gmail.com', createdAt: '2019-02-19T21:12:18.569Z', updatedAt: null, online: false, __v: 0 }, { friends: [], otherFriends: [], _id: '5c6ccd6d3a0dc4e4951c2bee', user: '5c65d9438e4a834c8e85dd7e', password: '$2b$10$gEAbOAdKyHJfAksr5txUNOudCautRs1w/pubplQKzZ5PefhfOOEhq', email: 'fdagssd@gmail.com', createdAt: '2019-02-20T03:45:49.703Z', updatedAt: null, online: false, __v: 0 }] newArray = initialArray.map(({ user }) => ({ user })); console.log(newArray); 

Answer 2

You can keep the desired keys in an array as follow.

This example extracts two key-values .

 var initialArray = [{ friends: [], otherFriends: [], _id: '5c6c7132f9bf4bdab9c906ff', user: '5c65d9438e4a834c8e85dd7d', password: '$2b$10$LMFB6CBdwxSAfjog/Uo3t.u/G0GBtzfJnYdpvlrSNchA9.jlNOdAa', email: 'sparky2df3dfdfdf2@gmail.com', createdAt: '2019-02-19T21:12:18.569Z', updatedAt: null, online: false, __v: 0 }, { friends: [], otherFriends: [], _id: '5c6ccd6d3a0dc4e4951c2bee', user: '5c65d9438e4a834c8e85dd7e', password: '$2b$10$gEAbOAdKyHJfAksr5txUNOudCautRs1w/pubplQKzZ5PefhfOOEhq', email: 'fdagssd@gmail.com', createdAt: '2019-02-20T03:45:49.703Z', updatedAt: null, online: false, __v: 0 }], keys = ["user", "email"], // for the desired output in the question remove "email" newArray = initialArray.map(o => keys.reduce((a, k) => Object.assign({}, a, {[k]: o[k]}), {})); console.log(newArray); 

 .as-console-wrapper { min-height: 100%; }