Filling up a 2D array with random numbers in javascript

Question

I'm really sorry if anything like this has been posted here before but I couldn't find anything, I'm kinda new to the site still!

So for a while now I've been learning a bit about game development through html5 and javascript and I stumbled upon making tileset maps, I now have a tileset and an 2D array that I want to put certain tiles in (the number varies between 6 and 10 in this case). I figured it could be a cool function to make the map choose between a small set of similar tiles so I don't have to specifically number every tile in the array(just define the type)

The method I have currently is probably the best for being able to define types but I want something that looks a bit cleaner and/or information to why my "cleaner" version dosen't work.

var ground = [
    [tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
    [tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
    [tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
    [tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
    [tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
    [tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
    [tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
    [tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
    [tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()]];

function tile() {
    var y = (Math.random() * 5 | 0) + 6;
    return y;
}

This is the code I've been using so far, I have to edit every element of the code with the tile() function to get a random number in each one, what I wanted to have was something like this:

for (var i = 0 ; i < 15; i++) {
    for (var j = 0; j < 9; j++) {
        ground[[i],[j]] = (Math.random() * 5 | 0) + 6;
    }
}

to fill the array without having to add the function to each spot.

I have a feeling that I'm missing a return function or something along those lines but honestly I have no idea.

ground[[i],[j]] = ground[i][j], and you have to create an array first and then push an value — A1rPun
– A1rPun, Commented Jul 28, 2014 at 22:55
I never did get ground[i][j] to work when initializing it, wich is hwy I'm using ground[[i],[j]] Oh and the double i++ was a typing error while I was making the question, sorry about that everyone! — Gatreh
– Gatreh, Commented Jul 28, 2014 at 23:31
ground[[i],[j]] can never work. [i],[j] outputs [2].. you are trying to get index [2] of ground. — A1rPun
– A1rPun, Commented Jul 28, 2014 at 23:37

A1rPun · Accepted Answer · 2017-02-13 16:13:31Z

10

You were thinking in the right direction but there are some errors in your code ;)

You have to initialize the array first before you can push elements into it.
And you were counting i++ twice

Javascript

var ground = []; // Initialize array
for (var i = 0 ; i < 15; i++) {
    ground[i] = []; // Initialize inner array
    for (var j = 0; j < 9; j++) { // i++ needs to be j++
        ground[i][j] = (Math.random() * 5 | 0) + 6;
    }
}

Maybe even better (reusable)

function createGround(width, height){
    var result = [];
    for (var i = 0 ; i < width; i++) {
        result[i] = [];
        for (var j = 0; j < height; j++) {
            result[i][j] = (Math.random() * 5 | 0) + 6;
        }
    }
    return result;
}
// Create a new ground with width = 15 & height = 9
var ground = createGround(15, 9);

edited Feb 13, 2017 at 16:13

answered Jul 28, 2014 at 23:01

A1rPun

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1 Comment

skribbz14 Over a year ago

Thank you so much! Initializing the inner array was the step I was forgetting to do and it had me scratching my head for a bit.

cgatian · Accepted Answer · 2014-07-28 23:01:53Z

1

Here's a quick example. I've created a function that will take in a width and height parameter and generate the size requested. Also I placed your tile function inside generate ground to keep it private, preventing other script from invoking it.

var ground = generateGround(10, 10); //Simple usage

function generateGround(height, width)
{
  var ground = [];
  for (var y = 0 ; y < height; y++) 
  {
    ground[y] = [];
    for (var x = 0; x < width; x++) 
    {
        ground[y][x] = tile();
    }  
  }
  return ground;

  function tile()
  {
    return (Math.random() * 5 | 0) + 6;
  }
}

http://jsbin.com/sukoyute/1/edit

answered Jul 28, 2014 at 23:01

cgatian

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Comments

colinmcp · Accepted Answer · 2014-07-28 22:54:59Z

0

Try removing the comma from...

ground[[i],[j]] = (Math.random() * 5 | 0) + 6;

...in your 'clean' version. Also, your incrementing 'i' in both for loops:

for (var i = 0 ; i < 15; i++) {
for (var j = 0; j < 9; i++) {

Hopefully these changes make it work for you :)

answered Jul 28, 2014 at 22:54

colinmcp

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