javascript class image.onload

Question

我在一個繪圖層工作，我需要製作Javascript類，它將在畫布上繪製圖像。現在，我有一些這樣的：

<canvas id="stage" width="1000" height="640"></canvas> 
    <script> 
     function ImageD(canvasId, imageSRC, X, Y, widht, height, Opacity) 
     { 
      var canvas; 
      var canvasInfo; 
      var opacity = Opacity || 1; 
      var image = new Image(); 

      var selectCanvas = function() 
      { 
       canvas = document.getElementById(canvasId); 
      }; 

      var get2dContext = function() 
      { 
       canvasInfo = canvas.getContext("2d"); 
      }; 

      this.draw = function() 
      { 
       selectCanvas(); 
       get2dContext(); 
       image.onLoad = function() 
       { 
        canvasInfo.drawImage(image, X, Y); 
       }; 
       image.src = imageSRC; 
      }; 
     } 

     var img = new ImageD("stage",  "http://www.nasa.gov/images/content/711375main_grail20121205_4x3_946-710.jpg", 20, 20, 30, 30); 
img.draw(); 
    </script> 

，並在控制檯我得到這個錯誤或通知......

資源解釋爲腳本，但使用MIME類型text/plain的轉移：.....

Answer 1

我修這跟如下代碼：

function ImageD(canvasId, imageSRC, X, Y, widht, height, Opacity) 
{ 
    var canvas; 
    var canvasInfo; 
    var opacity = Opacity || 1; 
    var image = new Image(); 

    var selectCanvas = function() 
    { 
     canvas = document.getElementById(canvasId); 
    }; 

    var get2dContext = function() 
    { 
     canvasInfo = canvas.getContext("2d"); 
    }; 

    var drawImg = function() 
    { 
     canvasInfo.drawImage(image, X, Y); 
    }; 

    this.draw = function() 
    { 
     selectCanvas(); 
     get2dContext(); 
     image.src = imageSRC; 
     image.addEventListener('load', drawImg, false); 
    }; 
}