How to remove a property from a JavaScript object?

You can use delete keyword to remove properties from objects.

if(myObject.hasOwnProperty('item1')) {
	delete myObject.item1;
}

Note that, To remove an element from an array, use Array.splice or Array.pop. For example:

arr // [0, 1, 2, 3, 4]
arr.splice(3,1); // 3
arr // [0, 1, 2, 4]

The delete keyword in JavaScript has a different function to that of the keyword in C and C++: it does not directly free memory. Instead, its only purpose is to delete properties from objects.

For arrays, removing a property corresponding to an index, creates a sparse array (ie. an array with a "hole" in it). Most browsers represent these missing array indices as "empty".

var array = [0, 1, 2, 3]
delete array[2] // [0, 1, empty, 3]

Different built-in functions in JavaScript handle sparse arrays differently.

• for...in will skip the empty index completely.
• A traditional for loop will return undefined for the value at the index.
• Any method using Symbol.iterator will return undefined for the value at the index.
• forEach, map and reduce will simply skip the missing index.

So, the delete keyword should not be used to removing elements from an array. Arrays have a dedicated methods for removing elements and reallocating memory: Array.splice() and Array.pop.

Array.splice(start[, deleteCount[, item1[, item2[, ...]]]])

let a = [0,1,2,3,4]
a.splice(2,2) // returns the removed elements [2,3]
// ...and `a` is now [0,1,4]

Array.slice([begin[, end]])

let a = [0,1,2,3,4]
let slices = [
    a.slice(0,2),
    a.slice(2,2),
    a.slice(2,3),
    a.slice(2,5) ]

//   a           [0,1,2,3,4]
//   slices[0]   [0 1]- - -   
//   slices[1]    - - - - -
//   slices[2]    - -[3]- -
//   slices[3]    - -[2 4 5]

Array.pop

Array.pop removes the last element from an array, and returns that element. This operation changes the length of the array.

Objects in JavaScript can be thought of as maps between keys and values. The delete operator is used to remove these keys.

var obj = {
  myProperty: 1    
}
console.log(obj.hasOwnProperty('myProperty')) // true
delete obj.myProperty
console.log(obj.hasOwnProperty('myProperty')) // false

Or, you can use object destructuring, an ECMAScript 6 feature, it's as simple as:

let myObject = {
  "item1": "value",
  "item2": "value",
  "item3": "value"
};
({ item1, ...myObject } = myObject);
console.log(myObject);