为什么这个JavaScript不在我的画布上画一个矩形呢?标签
Why isn’t this JavaScript drawing a rectangle in my <canvas> tag?
为什么不行?
<html>
<head>
<title>Learning the basics of canvas</title>
<meta charset="utf-8">
<script type="text/javascript" src="http://ajax.googleapis.com?/ajax/libs/jquery/1/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
var canvas = $("#myCanvas");
var context = canvas.get(0).getContext("2d");
context.fillRect(40, 40, 100, 100);
});
</script>
</head>
<body>
<canvas id="myCanvas" width="500" height="500">
<!-- Insert fallback content here -->
</canvas>
</body>
</html>
您的代码缺少一个文档类型,并且有一个错别字。
Doctype:
<!DOCTYPE html>
输入错误:
http://ajax.googleapis.com?/ajax/libs/jquery/1/jquery.min.js
应该http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js
固定代码:<!DOCTYPE html>
<html>
<head>
<title>Learning the basics of canvas</title>
<meta charset="utf-8">
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script>
//<![CDATA[
$(document).ready(function() {
var canvas = $("#myCanvas");
var context = canvas.get(0).getContext("2d");
context.fillRect(40, 40, 100, 100);
});
//]]>
</script>
</head>
<body>
<canvas id="myCanvas" width="500" height="500">
<!-- Insert fallback content here -->
</canvas>
</body>
</html>
您需要一个DOCTYPE。在页面最上方插入<!DOCTYPE html>
添加HTML 5 doctype标签。许多浏览器仍然默认呈现XHTML,并且需要您指出这是HTML 5格式。
http://www.w3schools.com/html5/tag_doctype.asp尝试canvas.getContext('2d')
,不包含中间的get(0)
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