creating 2d array in JavaScript

Question

I am a newbie at js and trying to create a 2D array but when I run the code I get in the console Array(10) [ <10 empty slots> ] even though I filled the array with values.
This is my js and HTML:

function Make2Darray(cols, rows) {
  let arr = new Array(cols);
  for (let i = 0; i < arr.lenght; i++) {
    arr[i] = new Array(rows);
    for (let j = 0; j < rows; j++) {
      arr[i][j] = floor(random(2));
    }
  }
  return arr;
}
let grid;
grid = Make2Darray(10, 10);
console.log(grid);

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1">

  <title>Game of Life</title>

  <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/[email protected]/lib/p5.min.js"></script>

  <script type="text/javascript" src="gol.js"></script>
</head>

<body>
</body>

</html>

At line 3 in the javascript portion, it should be arr.length. — Ahmad Habib
– Ahmad Habib, Commented Nov 6, 2020 at 14:07

Esteban MANSART · Accepted Answer · 2020-11-06 14:14:23Z

1

You made 2 mistakes : one the 3rd line, this is not arr.length that you want but cols Then, floor and random are parts of the Math lib provided by JS, so use it like this:

arr[i][j] = Math.floor(Math.random() * 2);

edited Nov 6, 2020 at 14:14

answered Nov 6, 2020 at 14:09

Esteban MANSART

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4 Comments

Nathan Chu Over a year ago

OP means Math.random()*2. Math.random takes 0 arguments. MDN

Esteban MANSART Over a year ago

Yep, i just copied his code and didn't noticed this, i edited

Heretic Monkey Over a year ago

Are you sure floor and random are not provided by p5.js? Because there are no errors in the snippet...

Esteban MANSART Over a year ago

GJ i didn't see P5 include

hco · Accepted Answer · 2020-11-06 14:17:01Z

0

I am not sure what you are trying to do with floor(random(2)) part, but you can create 2D array as below:

function Make2Darray(rows, cols) {
  let arr = []
 
  for (let i = 0; i < rows; i++) {
    arr[i] = []
    for (let j = 0; j < cols; j++) {
      arr[i][j] = Math.floor(Math.random()) // You can change the value in this part
    }
  }
 
  return arr
}

let grid = Make2Darray(10, 10)
console.log(grid)

answered Nov 6, 2020 at 14:17

hco

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