Question

我的代码就像这样

    <html>
  <head>
  </head>
  <body>
    <canvas id="myCanvas" width="578" height="200" style="display:none;"></canvas>
    <img id="canvasImg" onclick="myFunction()" alt="Right click to save me!">
    <script>
        var canvas = document.getElementById('myCanvas');
        var context = canvas.getContext('2d');
        function myFunction() {
            var c = document.getElementsByTagName("canvas");
            // save canvas image as data url (png format by default)
            var dataURL = c.toDataURL();
            // set canvasImg image src to dataURL
            // so it can be saved as an image
            document.getElementById('canvasImg').src = dataURL;
        }
    </script>
  </body>
</html>

当我点击canvasImg时抛出错误

Uncaught TypeError: Object #<NodeList> has no method 'toDataURL'

我做了fiddle here 任何人都可以指出什么是错的吗？

Answer 1

DEMO

document.getElementsByTagName返回元素对象的数组，没有数组对象具有方法toDataUrl

而不是

var c = document.getElementsByTagName("canvas");

使用

 var c = document.getElementsByTagName("canvas")[0];

Answer 2

    function myFunction() {
         var canvas = document.getElementById("myCanvas");
         var context = canvas.getContext("2d");
         var img = document.getElementById("canvasImg");
         context.drawImage(img, 0, 0);
    }

HTML5 Canvas没有方法＆＃39; toDataURL＆＃39;

2 个答案: