<canvas id="canvas" style="background:#111;width:100%;"></canvas>
<script>
window.onload = function(){
//获取画布对象
var canvas = document.getElementById("canvas");
//获取画布的上下文
var context = canvas.getContext("2d");
//获取浏览器的宽高
var W = window.innerWidth;
var H = window.innerHeight;
//设置canvas的宽高
canvas.width = W;
canvas.height = H;
//每个文字的大小
var fontSize = 16;
//计算浏览器一共可以放置多少列
var colunms = Math.floor(W / fontSize);
//记录每列文字的Y坐标
var drops = [];
//给每一个文字初始化一个起始点的位置
for(var i = 0;i<colunms;i++){
drops.push(0);
}
//要滚动的文字
var str = "javascript html5 canvas";
//4:fillText(str,x,y);原理就是去更改y的坐标位置
//绘画的函数
function draw(){
context.fillStyle = "rgba(0,0,0,0.05)";
context.fillRect(0,0,W,H);
//给字体设置样式
context.font = "700 "+fontSize+"px 微软雅黑";
//给字体添加颜色
context.fillStyle = "#00cc33";
//写入画布中
for(var i=0;i<colunms;i++){
var index = Math.floor(Math.random() * str.length);
var x = i*fontSize;
var y = drops[i]*fontSize;
context.fillText(str[index],x,y);
//如果要改变时间,肯定就是改变每次他的起点
if( y >= canvas.height && Math.random() > 0.99){
drops[i] = 0;
}
drops[i]++;
}
};
function randColor(){
var r = Math.floor(Math.random() * 256);
var g = Math.floor(Math.random() * 256);
var b = Math.floor(Math.random() * 256);
return "rgb(" + r +"," + g +"," + b +")";
}
draw();
setInterval(function(){
draw()
},30)
}
</script>