javascript canvas 实现下雪效果 圣诞节专用

直接引入以下JS代码就OK
原生JS，不需要JQuery

/* http://blog.csdn.net/jesounao */function r(a){return a*Math.random()}function s(){return document.createElement("canvas")}function u(){var a,d,e,f;for(p+=0.01,d=Math.sin(p),a=0;m>a;a++){f=o[a],e=Math.sin(4*p+a),f[1]+=f[2]/2+(2+e),f[0]+=6*(d+e/2)/(10/f[2]),f[1]>c&&(f[1]=-n,f[0]=r(b)),(f[0]>b||f[0]<-n)&&(f[0]=d>0?-n:b),o[a]=f}}function t(){var a,d;for(d=0;m>d;d++){a=0.6*m>d?0:0.8*m>d?1:0.9*m>d?2:0.98*m>d?3:4,o[d]=[r(b),r(c),a]}}function w(){b=window.innerWidth,c=window.innerHeight,void 0!==j&&(j.width=b,j.height=c,m=b*c/6000,l=k.createLinearGradient(0,0,0,c),t())}function t(){var a,d;for(d=0;m>d;d++){a=0.6*m>d?0:0.8*m>d?1:0.9*m>d?2:0.98*m>d?3:4,o[d]=[r(b),r(c),a]}}function v(){var a;for(k.fillStyle=l,k.clearRect(0,0,b,c),k.beginPath(),a=0;m>a;a++){k.drawImage(i[o[a][2]],o[a][0],o[a][1])}k.fill(),u()}function w(){b=window.innerWidth,c=window.innerHeight,void 0!==j&&(j.width=b,j.height=c,m=b*c/6000,l=k.createLinearGradient(0,0,0,c),t())}function x(){var a=!1;try{a=1}catch(b){}return a?(window.addEventListener("resize",w,!1),j=document.createElement("canvas"),j.style.position="fixed",j.style.top="0px",j.style.left="0px",j.style.zIndex=5000,j.style.pointerEvents="none",j.id="canvas_snow",document.body.appendChild(j),k=j.getContext("2d"),k.strokeStyle="none",d=s(),b=s(),f=s(),g=s(),h=s(),i=[d,b,f,g,h],y({canvas:d,width:0.4*n,height:0.4*n,color:"#FFF",soft:0.05}),y({canvas:b,width:0.5*n,height:0.5*n,color:"#FFF",soft:0.05}),y({canvas:f,width:0.6*n,height:0.6*n,color:"#FFF",soft:0.3}),y({canvas:g,width:0.8*n,height:0.8*n,color:"#FFF",soft:0.2}),y({canvas:h,width:n,height:n,color:"#FFF",soft:0.05}),w(null),snowTimer=setInterval(function(){q(v)},50),void 0):!1}function z(a,b){var c,d,e;return a=a.replace(/^s*#|s*$/g,""),3===a.length&&(a=a.replace(/([0-9a-fA-F])/g,"$1$1")),d=parseInt(a.substr(2,2),16),e=parseInt(a.substr(4,2),16),c=parseInt(a.substr(0,2),16),"rgba("+c+", "+d+", "+e+", "+b+")"}function y(a){var b,c,d,e,f,g,h,i,j;d=a.width||30,e=a.height||30,f=d/2,g=e/2,i=a.color||"#FFF",h=a.soft||0,b=a.canvas,b.width=d,b.height=d,c=b.getContext("2d"),c.clearRect(0,0,d,e),j=c.createRadialGradient(f,g,0,f,g,f),j.addColorStop(0,i),j.addColorStop(0.1,i),j.addColorStop(0.85,z(i,h)),j.addColorStop(1,z(i,0)),c.fillStyle=j,c.fillRect(0,0,d,e)}var b,c,d,e,f,g,h,i=[],j,k,l,m,n=20,o=[],p=0,q=function(){return window.requestAnimationFrame||window.webkitRequestAnimationFrame||window.mozRequestAnimationFrame||window.oRequestAnimationFrame||window.msRequestAnimationFrame||function(a){window.setTimeout(a,62.5)}}();x();