Javascript - removing undefined fields from an object [duplicate]

Question

A one-liner using ES6 arrow function and ternary operator:

Object.keys(obj).forEach(key => obj[key] === undefined ? delete obj[key] : {});

Or use short-circuit evaluation instead of ternary: (@Matt Langlois, thanks for the info!)

Object.keys(obj).forEach(key => obj[key] === undefined && delete obj[key])

Same example using if statement:

Object.keys(obj).forEach(key => {
  if (obj[key] === undefined) {
    delete obj[key];
  }
});

If you want to remove the items from nested objects as well, you can use a recursive function:

const removeEmpty = (obj) => {
  let newObj = {};
  Object.keys(obj).forEach((key) => {
    if (obj[key] === Object(obj[key])) newObj[key] = removeEmpty(obj[key]);
    else if (obj[key] !== undefined) newObj[key] = obj[key];
  });
  return newObj;
};

I prefer to use something like Lodash:

import { pickBy, identity } from 'lodash'

const cleanedObject = pickBy(originalObject, identity)

Note that the identity function is just x => x and its result will be false for all falsy values. So this removes undefined, "", 0, null, ...

If you only want the undefined values removed you can do this:

const cleanedObject = pickBy(originalObject, v => v !== undefined)

It gives you a new object, which is usually preferable over mutating the original object like some of the other answers suggest.

var obj = { a: 1, b: undefined, c: 3 }

To remove undefined props in an object we use like this

JSON.parse(JSON.stringify(obj));

Output: {a: 1, c: 3}

Because it doesn't seem to have been mentioned, here's my preferred method, sans side effects or external dependencies:

const obj = {
  a: 1,
  b: undefined
}

const newObject = Object.keys(obj).reduce((acc, key) => {
  const _acc = acc;
  if (obj[key] !== undefined) _acc[key] = obj[key];
  return _acc;
}, {})

console.log(newObject)
// Object {a: 1}

This solution also avoids hasOwnProperty() as Object.keys returns an array of a given object's own enumerable properties.

Object.keys(obj).forEach(function (key) {
 if(typeof obj[key] === 'undefined'){
    delete obj[key];
  }
});

and you can add this as null or '' for stricter cleaning.