delete Removes key from 2 objects

Question

I have 2 objects: one of them contains the player list and the other one contains players in loading screen.

When i remove a player from playersNotReady object, it also removes the player from the player list and i don't want that.

var players = {
  1: "Player1",
  2: "Player2"
};
var playersNotReady = players;
delete playersNotReady[1];
console.log(players); // {2: "Player2"}
console.log(playersNotReady); // {2: "Player2"}

Why is this happening and how can i remove player from playersNotReady object without removing them from the actual player list?

You have to clone the object for playersNotReady because players and playersNotReady share the same object. — Powkachu, Mar 28 '18 at 08:58
*"Why is this happening?"* -- the statement `var playersNotReady = players;` does not duplicate the value of `players`. It just adds a new reference to it. The object you create in the first lines of code can now be accessed through two variables: `players` and `playersNotReady`. — axiac, Mar 28 '18 at 08:59

Eddie · Accepted Answer · 2018-03-28T12:37:27.153

You are not creating a new variable. You are just pointing by reference. You can use Object.assign to clone/create new object.

var players = {
  1: "Player1",
  2: "Player2"
};
var playersNotReady = Object.assign({}, players);
delete playersNotReady[1];
console.log(players); 
console.log(playersNotReady);

Doc: Object.assign

One option also, is to use Destructuring Assignment, Like:

var players = {
  1: "Player1",
  2: "Player2"
};
var {1: p1,...playersNotReady} = players; //This will create a new object and remove the 1
console.log(players);
console.log(playersNotReady);

Doc: Spread

score 0 · Answer 2 · answered Mar 28 '18 at 09:01

When you do var playersNotReady = players; you are not creating a new object, but simply a new reference to the players object, this is because objects are passed by reference in javascript.

To create a new object, you can use the ES6 spread operator: var playersNotReady = {...players};

score 0 · Answer 3 · answered Mar 28 '18 at 09:03

while you assign var playersNotReady = players; it actually create a reference for players. not a new object. You can copy object by Object.assign.

var players = {
  1: "Player1",
  2: "Player2"
};
var playersNotReady = Object.assign({}, players);
delete playersNotReady[1];
console.log(players); // {2: "Player2"}
console.log(playersNotReady); // {2: "Player2"}

delete Removes key from 2 objects

3 Answers3