Creating a 2D array in Javascript with the values as the product of the indices

Question

I got a problem which says:

Write a program which takes 2 digits, X,Y as input and generates a 2-dimensional array. The element value in the i-th row and j-th column of the array should be i*j. Note: i=0,1.., X-1; j=0,1,¡­Y-1. Example Suppose the following inputs are given to the program: 3,5 Then, the output of the program should be: [[0, 0, 0, 0, 0], [0, 1, 2, 3, 4], [0, 2, 4, 6, 8]]

.....

I write the following code for it:

var main=[]
function array(x,y){
    var n=x
    while(n<0){
        main.push([0])
        n-=1
    }

    for(let i=0 ; i<x ; i+=1){
        for (let j=0 ; j=y ; j+=1){
            main[i].push(i*j)
        }
        main[i].shift()
    }
    return main
}
console.log(array(2,2))

but I am getting an error in running it in VScode. please guide me

Answer 1

It's not necessary to push to the array. You can write directly to the x and y index of the target array, as long as array[x] itself is an array.

What you can do is for each x of width (the first array level) you can create an array of size y and then write x*y values into its elements.

There's probably a faster way of doing this but I find the following to be the most readable.

function make2DArray(width, height) {
  const array = Array(width);
  for (let x=0; x<width; x++){
    array[x] = Array(height);
    for (let y=0; y<height; y++){
      array[x][y] = x*y;
    }
  }
  return array;
}