How to update only the given index of 2d array in javascript?

Question

I created a 2d array using Array constructor and filling it with a array inside it.

const a = new Array(26).fill(new Array(2).fill(-1));

When i try to do this a[0][0] = 0 the 0th index of all 26 arrays have changed. How do I prevent that?

const a = new Array(26).fill(new Array(2).fill(-1));
a[0][0] = 0

console.log(a)

[_"If the first parameter is an object, each slot in the array will reference that object."_](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/fill). — Andy, Sep 12 '21 at 06:33
`Array.from({ length: 26 }, () => new Array(2).fill(-1))` This will also work — DecPK, Sep 12 '21 at 06:40

Yosvel Quintero · Accepted Answer · 2021-09-12T06:46:13.153

1

Try this:

const a = [...Array(26)].map(() => new Array(2).fill(-1))
a[0][0] = 0

console.log(a)

edited Sep 12 '21 at 06:46

answered Sep 12 '21 at 06:35

Yosvel Quintero

1 Answers1