matrix, iterator and symmetric matrix

matrix-iterable.js

class Matrix {
  constructor(width, height, element = (x, y) => undefined) {
    this.width = width;
    this.height = height;
    this.content = [];
    for(let y = 0; y < height; y++) {
      for(let x = 0; x < width; x++) {
        this.content[y * width + x] = element(x, y);
      }
    }
  }
  
  get(x,y){
    return this.content[y * this.width + x];
  }
  
  set(x,y, value) {
    this.content[y * this.width + x] = value;
  }
  
  [Symbol.iterator]() {
    return new MatrixIterator(this)
  }
}

class SymmetricMatrix extends Matrix {
  constructor(size, element = (x,y) => undefined) {
    super(size, size, (x,y) => {
      if(x < y) return element(y,x)
      else return element(x,y)
    })
  }
  
  set(x, y, value) {
    super.set(x, y, value)
    if(x !== y) super.set(y, x, value)
  }
}

class MatrixIterator {
  constructor(matrix) {
    this.x = 0;
    this.y = 0;
    this.matrix = matrix;
  }
  
  next(){
    if(this.y === this.matrix.height) return {done: true}
    const value = {
      x: this.x,
      y: this.y,
      value: this.matrix.get(this.x, this.y)
    }
    this.x++;
    if(this.x === this.matrix.width) {
      this.x = 0;
      this.y++
    }
    return {value, done: false}
  }
}

const matrix = new Matrix(2,2, (x,y)=>`value: (${x}, ${y})`);
for(let {x,y,value} of matrix){
  console.log(x, y, value)
}

const symmetricMatrix = new SymmetricMatrix(5, (x,y)=>`value: (${x}, ${y})`);
console.log(symmetricMatrix.get(2, 3));