Initializing a 2D Array with a Ton of Zeroes

[ItsYaBoiWesley]

Hi! I'm trying to make a 2D array with a ton of zeroes. For some reason, this does not work. (By does not work, I mean I get errors when accessing the array. If I initialize the array manually, it's smooth sailing.)

  var blankRow = [];

  for(var x = 0; x < world[0].length; x++) {
    blankRow.push(0);
  }
  for(var y = 0; y < world.length; y++) {
    processedWorld.push(blankRow);
  }

 

It pushes the blank row full of zeroes (the horizontal axis) then pumps that into the destination array (processedWorld, the vertical axis)

What am I screwing up

P.S. "world" is a different array from "processedWorld" and has already been defined, and works perfectly.

[b10b]

Looks like you're pushing the same blankRow into all the rows.  So any change to any row will effect all rows.  Whereas you probably want to push a new bankRow into each row?  Solution: move the x loop into the y loop.

You may also want to consider an alternative data structure to an array if you're doing higher level manipulation.

[ItsYaBoiWesley]

This worked, thanks!

[mattstyles]

The most simple way is probably:

const DIM = 100
const map = new Array(DIM).fill(0)

For the 2D variant you're using:

const X_SIZE = 4
const Y_SIZE = 2
const map = new Array(X_SIZE).fill(new Array(Y_SIZE).fill(0))

// Better:
function createArray (length, fill) {
  return new Array(length).fill(fill)
}

const map = createArray(X_SIZE, createArray(Y_SIZE, 0))

Depending on your coordinate system you might want to invert X and Y.

Note that fill is really naive, I normally use some other helpers that allow a 'fill' function to accept a function which allows a really nice clean API for creating simple or complex arrays.