Modifying one array modifies another one I made from it

Question

var allCoords = [{ x: 2, y: 3 }, { x: 3, y: 4 }];
var emptySpaces = allCoords;

emptySpaces.splice(0, 1);
console.log(allCoords.length);
console.log(emptySpaces.length);

I do not understand why both of these output "1". Why is the original array, allCoords being modified, when I only want the second one, emptySpaces to be edited?

the simple answer is they are the same array. `emptySpaces = allCoords` creates a reference , not a copy — charlietfl, Dec 06 '14 at 06:44

score -1 · Accepted Answer · answered Dec 06 '14 at 05:21

-1

Modify your code like this:

(function testing() {
    var allCoords = [];
    var emptySpaces = allCoords.slice();

    emptySpaces.push({
        x: 1,
        y: 2
    });
    console.log(allCoords.length);
    console.log(emptySpaces.length);
}());

answered Dec 06 '14 at 05:21

Verhaeren

1,661
9
10

In this example anyway, `allCoords.slice()` should just be `[]`. No reason to clone an empty array. – Alexander O'Mara Dec 06 '14 at 05:23

Modifying one array modifies another one I made from it

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