How to fix the error of undefined 'x'?

Question

JavaScript

I want to write a game, through prototype, but in the console there is an error

Code:

;(function(){

let canvas, ctx, width, height;

let Game = function(){
    
    //Подключаюсь к canvas.
  canvas = document.getElementById('knight');

  ctx = canvas.getContext('2d');

  let gameSize = {

  };

  this.loadGame();

  this.knight = new knight();

}

const bg = new Image();

bg.src = "img/bg.png";

Game.prototype.loadGame = function(){
  this.knight();
  this.draw();

  requestAnimationFrame(()=>{
    this.loadGame();
  });
}

function knight(){
  this.size = {x : 150, y : 150};
  this.position = {x : 150, y : 150};
}


Game.prototype.knight = function(){

}

Game.prototype.draw = function(){
  ctx.fillRect(150, 150, this.size.x, this.size.x)
}

window.onload = function(){
  new Game("ctx");
}

})();

Answer 1

You have something scary here :(
At a minimum, please adjust the indents.
1. You call the loadGame function, it is taken from Game.prototype.
2. loadGame calls the this.knight function - it is also selected from Game.prototype (empty function)
3. The draw function is called, this.size.x is used - and this.size - does not exist, this field is not filled in. The
question was how to fix it - I have no idea what you want, maybe in the Game.prototype.knight declaration you need to drag the implementation of knight (normal function).