代码如下 快去使用吧！
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<canvas id="q"></canvas>
<script type="text/javascript" >
var s = window.screen;
var width = q.width = s.width;
var height = q.height = s.height;
var letters = Array(256).join(1).split('');
var draw = function () {
q.getContext('2d').fillStyle='rgba(0,0,0,.05)';
q.getContext('2d').fillRect(0,0,width,height);
q.getContext('2d').fillStyle='#0F0';
letters.map(function(y_pos, index){
text = String.fromCharCode(3e4+Math.random()*33);
x_pos = index * 10;
q.getContext('2d').fillText(text, x_pos, y_pos);
letters[index] = (y_pos > 758 + Math.random() * 1e4) ? 0 : y_pos + 10;
});
};
setInterval(draw, 33);
</script>
</body>
</html>
