js 'getContext' of null

Uncaught TypeError: Cannot read property 'getContext' of null
才接触js,网上搜了很久没找到有用的,为什么我这个图片加载不出来

 <!DOCTYPE html>
<html lang="en" dir="ltr">
  <head>
    <meta charset="utf-8">
    <title>哈哈哈哈哈</title>
  </head>
  <body>
    <canvas id="'myCanvas" width="200" height="400"style="border:1px solid #c3c3c3;">
    </canvas>

      <script>

      var canvas = document.getElementById('myCanvas');
      var context = canvas.getContext('2d');

      var img = new Image();

      img.onload = function(){
        context.drawImage(img,0,0);
      };
      img.src='uu.png';
      </script>

  </body>

</html>

ID错误了啊。。。多了个单引号。。

  <canvas id="myCanvas"

你把img.src='uu.png';放到img.onload上面看下。如果还不可以检查下你的图片路径。

var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');

var img = new Image();
img.src='uu.png';
img.onload = function(){
context.drawImage(img,0,0);
};

你ID多了个单引号。。

id="'myCanvas" 引号错了哦