Help a poor noob - arrays

[josephh]

Hi,

Welcome to the forum!

Your error comes from the fact that you are assigning stage1 to the variable fase before the variable stage1 has been initialized.

The computer reads your program from top to bottom but in JavaScript it doesn’t give you an error. You can refer to this previous thread on the subject :

We have to claim variables in advance?

Interestingly, if I claim variable like function setup() { createCanvas(100,100); let pg = createGraphics(100,100); // claim variable like this } function draw() { pg.background(100); image(pg, 0, 0); } when I call pg.background(100), the error occurs “pg is not defined”. But if I claim it in advance like let pg; function setup() { createCanvas(100,100); pg = createGraphics(100,100); // claim variable like this } function draw() { pg.background(100); image(pg, 0, 0); } i…

This is what happens :

1. The JavaScript engine parse your code. Because of hoisting, it moves the declaration of the stage1 variable so it’s doing :

var stage1; // Uninitialized -> undefined

2. Then we declare and assign stage1 to fase which is undefined:

var fase = stage1; // -> undefined

3. The stage1 variable gets initialized with the array :

var stage1 = [
  [‘0’, ‘1’, ‘0’, ‘1’],
  [‘0’, ‘1’, ‘1’, ‘0’],
];

But fase is still undefined!!

Check out this simple example :

var a = b;
console.log(a); // Prints undefined

var b = [0, 1];
console.log(a, b); // Prints undefined [0, 1]

So you need to assign stage1 to fase after stage1 has been initialized