我要评论本文实例为大家分享了js+canvas实现下雪效果的具体代码，供大家参考，具体内容如下
效果展示：
源码展示:
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>canvas下雪效果(原生js)</title>
<style>
* {
margin: 0;
padding: 0
}
html, body {
width: 100%;
height: 100%;
overflow: hidden;
background-color: #222;
}
#canvas {
position: absolute;
top: 0;
left: 0;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<img id="imgsnow" width="0" height="0" src="xh.png" alt="雪花">
<img id="bgsnow" width="100%" height="100%" src="bj.jpg" alt="背景">
<script>
window.onload = function () {
var canvas = document.getelementbyid("canvas");
var imgsnow = document.getelementbyid("imgsnow");
var bgsnow = document.getelementbyid("bgsnow");
var ctx = canvas.getcontext('2d');
var mbody = document.queryselector("body");
canvas.width =mbody.offsetwidth;
canvas.height = mbody.offsetheight;
var getrandomnum = function (min, max) {
var range = max - min;
var rand = math.random();
return (min + math.round(rand * range));
}
// console.log(getrandomnum(0, canvas.width))
var snowarray = {}; //雪花对象
var snowindex = 0; //标识符
var setting = {
num: 30, //数量
snowsize: 20, //大小
startx: math.random() * canvas.width, //起始横坐标
starty: 0, //起始纵坐标
vy: 0.01
}
function snow() {
// 起始横坐标
this.x = math.random() * canvas.width;
// 起始纵坐标
this.y = setting.starty;
this.size = setting.snowsize + math.random() * 10 - 10;
//横坐标偏移量
this.vx = math.random() * 3 - 2; //偏移量
//纵坐标偏移量
this.vy = math.random() * 10;
this.life = 0;
this.maxlife = 100;
this.id = snowindex;
//当前信息保存至对象snowarray
snowarray[snowindex] = this;
snowindex++;
}
snow.prototype.draw = function () {
this.x += this.vx;
this.y += this.vy;
this.vy += setting.vy;
this.life++;
//删除
if (this.y > canvas.height * 0.9 - 20) {
snowarray[this.id]
} else if (this.life >= this.maxlife) {
snowarray[this.id]
}
ctx.drawimage(imgsnow, this.x, this.y, this.size, this.size)
}
setinterval(function () {
ctx.drawimage(bgsnow, 0, 0, canvas.width, canvas.height);
//数
for (var i = 0; i < setting.num; i++) {
if (math.random() > 0.97) {
new snow();
}
}
for (var i in snowarray) {
snowarray[i].draw();
}
}, 100)202082104246954
}
</script>
</body>
</html>
图片：
雪花：
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持移动技术网。
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