// var gameArea = {
//   canvas : document.createElement("canvas"),
//   start  : function () {
//     this.canvas.width = 800;
//     this.canvas.height = 600;
//     this.context = this.canvas.getContext("2d");
//     document.body.insertBefore(this.canvas , document.body.childNodes[0]);
//     this.frameNo = 0;
//     console.log("start gameArea");
//   },
//   clear : function() {
//     this.context.clearRect ( 0 , 0 , this.canvas.width , this.canvas.heigth);
//   }
//
// }

class GameArea {
  constructor(canvas = document.createElement("canvas")) {
    this.canvas = canvas;
  }
  start(){
    this.canvas.width = 800;
    this.canvas.height = 600;
    this.context = this.canvas.getContext("2d");
    document.body.insertBefore(this.canvas , document.body.childNodes[0]);
    this.frameNo = 0;
    console.log("start gameArea");
  }
  clear(){
    this.context.clearRect ( 0 , 0 , this.canvas.width , this.canvas.heigth);
  }
}

@@ -850,24 +850,26 @@
 lear()%7B%0A    
+  
 this.context
@@ -925,18 +925,18 @@
 vas.heig
-t
 h
+t
 );%0A  %7D%0A%7D

fix typo