Reduce key value pairs in a javascript object based on a given array

Question

I want to remove unnecessary key values pairs in a user object based on an array, essentially a whitelist. I have looked at reduce(), filter() and map() but can't quite get the implementation to work.

Here is my code currently

const user = {
   "email": "[email protected]"
   "name": "Bob"
   "surname": "Smith"
};

const userFields = [`email`, `name`]; // array of whitelist

Before I iterate through the object properties, I'd like to reduce Object to have fields only in the array whitelist, so our man Bob Smith would end up like this

const user = {
  "email": "[email protected]" 
  "name": "Bob"
};

Thanks!

Question: Do you want to modify the object in place, or create a new object? — Barmar
– Barmar, Commented Jan 14, 2021 at 16:36

Siva Kondapi Venkata · Accepted Answer · 2021-01-14 16:41:15Z

1

Use reduce on userFields and build

const user = {
  email: "[email protected]",
  name: "Bob",
  surname: "Smith",
};

const userFields = [`email`, `name`];

const newUser = userFields.reduce(
  (acc, key) => Object.assign(acc, { [key]: user[key] }),
  {}
);
console.log(newUser)

answered Jan 14, 2021 at 16:41

Siva Kondapi Venkata

11.1k2 gold badges20 silver badges32 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

T.J. Crowder · Accepted Answer · 2021-01-14 16:54:04Z

0

For me, the simplest thing to do would be to loop through the passlist and build an object:

const result = {};
for (const name of userFields) {
    result[name] = user[name];
}

Live Example:

const user = {
   "email": "[email protected]",
   "name": "Bob",
   "surname": "Smith",
};

const userFields = [`email`, `name`];

const result = {};
for (const name of userFields) {
    result[name] = user[name];
}

console.log(result);

You could use map and Object.fromEntries, but I don't think it buys you anything:

const result = Object.fromEntries(
    userFields.map(name => [name, user[name]])
);

Live Example:

const user = {
   "email": "[email protected]",
   "name": "Bob",
   "surname": "Smith",
};

const userFields = [`email`, `name`];

const result = Object.fromEntries(
    userFields.map(name => [name, user[name]])
);

console.log(result);

FWIW, for me reduce is the wrong tool for this (or indeed, almost anything else outside of Functional Programmning with predefined, reusable reducer functions), not least because the accumulator in a reduce solution would never change (it's always the same object). reduce where a simple loop suffices is just overcomplicated and easy to get wrong. (An opinion which isn't solely mine, btw.)

edited Jan 14, 2021 at 16:54

answered Jan 14, 2021 at 16:37

T.J. Crowder

1.1m201 gold badges2k silver badges2k bronze badges

1 Comment

T.J. Crowder Over a year ago

@VLAZ - LOL, quite. What was I thinking?!

phi-rakib · Accepted Answer · 2021-01-14 17:09:18Z

0

You could use Object.fromEntries() method. Traverse the userFields array using Array.prototype.map() and make a list of key-value pair array. At last, from that list transform it into the required object by using Object.entries() method.

const user = {
  email: '[email protected]',
  name: 'Bob',
  surname: 'Smith',
};

const userFields = [`email`, `name`];
const ret = Object.fromEntries(userFields.map((x) => [x, user[x]]));
console.log(ret);

edited Jan 14, 2021 at 17:09

answered Jan 14, 2021 at 16:47

phi-rakib

3,3222 gold badges12 silver badges21 bronze badges

Collectives™ on Stack Overflow

Reduce key value pairs in a javascript object based on a given array

3 Answers 3

Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related