For in Javascript Array 3d

Question

I want initialize an array 3d with zeros in all positions. i am using a for cycle for filling my matrix but when I tested, I get an error TypeError: this.matrix[x][y] is undefined I have this:

class Cube {

    constructor(size) {
        this.size = size
        this.matrix = [ [ [] ], [ [] ] ]
        this.createMatrix(size)
    }

    getsize() {
        return this.size
    }

    /*Fill matrix with zeros*/
    createMatrix(size) {
        for (var x = 0; x < size; x++) {
            for (var y = 0; y < size ; y++) {
                for (var z = 0; z < size ; z++) {
                   this.matrix[x][y][z] = 0
                }
            } 
        }
        console.log(this.matrix)
    }
 }

 myCube = new Cube(4)

How Can I fill my matrix?

Answer 1

That's because you need to initialize each individual array. Remember: a 3D array is an array of arrays of arrays .

 function threeDArray(width, height, depth) { var result = []; for (var x = 0; x < width; x++) { result[x] = []; for (var y = 0; y < height; y++) { result[x][y] = []; for (var z = 0; z < depth; z++) { result[x][y][z] = 0; } } } return result; } console.log(threeDArray(3, 3, 3)); 

Answer 2

You will have to check every item in the array if it wasn't initialized yet, and in such case you will need to set it to Array :

 class Cube { constructor(size) { this.size = size this.matrix = [ ] this.createMatrix(size) } getsize() { return this.size } /*Fill matrix with zeros*/ createMatrix(size) { for (var x = 0; x < size; x++) { for (var y = 0; y < size ; y++) { for (var z = 0; z < size ; z++) { if (!Array.isArray(this.matrix[x])) { this.matrix[x] = [] } if (!Array.isArray(this.matrix[x][y])) { this.matrix[x][y] = [] } if (!Array.isArray(this.matrix[x][y][z])) { this.matrix[x][y][z]= [] } this.matrix[x][y][z] = 0 } } } console.log(this.matrix) } } myCube = new Cube(4) 

Answer 3

You can use Array.from({ length: n }) to create empty arrays of n length, and fill them with zeros using the fill() method:

 const emptyArray = n => Array.from({ length: n }); const createMatrix = n => emptyArray(n).map(() => emptyArray(n).map(() => emptyArray(n).fill(0)) ); console.log(createMatrix(4));