Assigning to multidimensional arrays javascript

Question

I have arrays within objects full of false values.

var drumOn = {}, bassOn = {}, synthOn = {}, keysOn = {};
var fal = [];    
for(var j=0; j<16; j++){
  fal.push(false);
}

for(var j=0; j<0; j++){
  drumOn['s'+j] = (fal);
  bassOn['s'+j] = (fal);
  synthOn['s'+j] = (fal);
  keysOn['s'+j] = (fal);
}

then later I try adding one true value to one array

drumOn['s'+ 0][0] = true;

This adds a true value to the first element of all the arrays within drumOn and within the other objects too.

The only other thing I'm doing with these objects is checking

    if(bassOn['s' + i][j])

I was doing this with arrays within arrays and I had the same problem.

This is crazy, I've tried so many things but it makes no sense.

You are loading the objects all with the same array. They all reference the same fal array. So, when you edit one, they all get edited. — gen_Eric
– gen_Eric, Commented Feb 17, 2016 at 21:58

Community · Accepted Answer · 2017-05-23 12:31:10Z

3

Copying array by value in JavaScript

for(var j=0; j<0; j++){
  drumOn['s'+j] = fal.slice();
  bassOn['s'+j] = fal.slice();
  synthOn['s'+j] = fal.slice();
  keysOn['s'+j] = fal.slice();
}

slice returns a copy of the array. In your example, all of the items are pointing to the same original array fal. You need to duplicate it.

edited May 23, 2017 at 12:31

CommunityBot

11 silver badge

answered Feb 17, 2016 at 21:59

Jeff

25.3k4 gold badges73 silver badges79 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Assigning to multidimensional arrays javascript

1 Answer 1

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Linked

Related