Defining 2D array Javascript

Question

Hi I am attempting to define a 2D array in JS but I seem to get two errors preventing me and I am not sure where I am going wrong. i is simply from a for loop - it has been defined. Even if I replace i with 0 same error occurs. My code:

let leds[i][i] = randint(0, 10);

This results in the error:

'=' expected.

however removing the let:

leds[i][i] = randint(0, 10);

results in a different error:

Type 'number' is not assignable to type 'undefined'.

I am using the JS editor for the BBC Microbit. Thanks in advance.

Answer 1

The variable leds needs to be defined as an array before it can be used as one. Then you can add elements to it using the push method; and these elements can be other (nested) arrays. For example:

//set leds as an empty array
let leds = [];

//add to the array
leds.push([]);
leds[0] = [1,2,3];

leds.push([]);
leds[1] = [4,5,6];

leds.push([7,8,9]);

//change an array value
leds[1][1] = 0;

console.log(leds);