text: (function () {
  
      var canvas = document.getElementById('canvas');
  
      var DrawShape = (function () {
  
          function DrawShape(canvas) {
              this.canvas = canvas;
              this.c = this.canvas.getContext('2d');
          }
  
          DrawShape.prototype = {
              drawCircle: function
                  (x, y, radius) {
                  this.x = x;
                  this.y = y;
                  this.r = radius;
                  this.c.beginPath();
                  this.c.arc(this.x, this.y, this.r, 0, 2 * Math.PI);
                  this.c.fillStyle = 'blue';
                  this.c.fill();
                  console.log('circle')
              },
              drawRect: function (x, y, width, height) {
                  this.x = x;
                  this.y = y;
                  this.width = width;
                  this.height = height;
                  this.c.fillStyle = 'red';
                  this.c.fillRect(this.x, this.y, this.width, this.height);
  
                  console.log('rect')
              },
              drawLine: function (x1, y1, x2, y2) {
                  this.x1 = x1;
                  this.y1 = y1;
                  this.x2 = x2;
                  this.y2 = y2;
  
                  this.c.beginPath();
                  this.c.moveTo(this.x1, this.y1);
                  this.c.lineTo(this.x2, this.y2);
                  this.c.strokeStyle = 'green';
                  this.c.stroke();
              }
  
          }
  
  
          return DrawShape;
      })();
  
      var module = new DrawShape(canvas);
      module.drawCircle(30,30,50);
      module.drawLine(1,2,800,500);
      module.drawRect(40,40,500,500)
  
  
  })();