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?

Dekel · Accepted Answer · 2017-01-16 20:50:48Z

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)

edited Jan 16, 2017 at 20:50

answered Jan 16, 2017 at 20:46

Dekel

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3 Comments

Mike Cluck Over a year ago

Note: typeof is not a function so parentheses are not required and typeof [] will return "object" so it's not a good method for checking if something is an array.

Dekel Over a year ago

@MikeC thanks for the comment! Changed to Array.isArray instead of typeof

Carmoreno Over a year ago

Thanks @Dekel, your answer was useful for me.

Mike Cluck · Accepted Answer · 2017-01-16 20:45:56Z

2

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));

answered Jan 16, 2017 at 20:45

Mike Cluck

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Comments

Michał Perłakowski · Accepted Answer · 2017-01-16 20:51:01Z

2

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));

answered Jan 16, 2017 at 20:51

Michał Perłakowski

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