CODEWITHSUNDEEP
javascript
Shwmae
Shwmae

Reputation: 91

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

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!

Upvotes: 1

Views: 1008

Answers (3)

phi-rakib
phi-rakib

Reputation: 3302

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);

Upvotes: 0

T.J. Crowder
T.J. Crowder

Reputation: 1074305

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.)

Upvotes: 0

Siva Kondapi Venkata
Siva Kondapi Venkata

Reputation: 11001

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)

Upvotes: 1

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