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<html>
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<head>
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<meta charset="utf-8">
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<title>菜鸟教程(runoob.com)</title>
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</head>
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<body>
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<canvas id="myCanvas" width="200" height="200" style="border:1px solid">
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您的浏览器不支持 HTML5 canvas 标签。
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</canvas>
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<br>
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<script>
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var c = document.getElementById("myCanvas");
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var ctx = c.getContext("2d");
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ctx.fillStyle = "#92B901";
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ctx.fillRect(50, 50, 100, 100);
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function clearCanvas() {
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c.height = 300;
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}
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</script>
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<button onclick="clearCanvas()">清空画布</button>
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</body>
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</html>