remove undefined from object javascript code example

Example 1: js remove undefined from object

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

Example 2: remove undefined from object js

const buildAnObjectFromAQuery = query => (
  {  
   ...query.foo && { foo: query.foo },  
   ...query.bar && { bar: query.bar },
  }
);

Example 3: remove undefined values from object javascript

var obj = { a: 1, b: undefined, c: 3 }
console.log(JSON.parse(JSON.stringify(obj)));
Output: {a: 1, c: 3}

Example 4: delete object property vs undefined assignment javascript

a.x = undefined
a.hasOwnProperty("x") // returns true

delete a.x
a.hasOwnProperty("x") // returns false