JavaScript實現小球碰撞特效。類似自由落體運動。實現原理非常簡單，就是動態的改變每個元素的坐標。使用radius屬性將圖片圓角化。使用left，top屬性動態的改變小球的位置。碰撞反彈球，當碰撞到容器的邊緣后，進行反彈，反向改變坐標。
首先創建Screen類，并在Screen的構造函數中給出了球移動、碰撞所需的各種屬性變量，如ballsnum、spring、bounce、gravity等等 ?然后用原型prototype給出相應的函數，如創建球，createBalls，球碰撞hitBalls，球移動moveBalls，給每個函數添加相應的功能、
最后用按鈕點擊事件調用函數，僅此而已。只是我這里把點擊的效果注釋掉了，直接刷新頁面就會隨機改變。
運行效果如下：
html代碼如下：html>
業余草：www.xttblog.combody?{
margin:0;
padding:0;
text-align:?center;
}
#screen?{?width:?800px;?height:?640px;?position:?relative;?background:?#ccccff;margin:?0?auto;vertical-align:?bottom}
#inner?{?position:?absolute;?left:0px;?top:0px;?width:100%;?height:100%;?}
#screen?p?{color:white;font:bold?14px;}
.one?{?background:url('images/QP1.png')?no-repeat;?background-size:?100%?auto;}
.two?{?background:url('images/QP2.png')?no-repeat;?background-size:?auto?100%;}
.three?{?background:url('images/QP3.png')?no-repeat;?background-size:?auto?100%;?}
.four?{?background:url('images/QP4.png')?no-repeat;?background-size:?auto?100%;}
.five?{?background:url('images/QP5.png')?no-repeat;?background-size:?auto?100%;}
.six?{?background:url('images/QP6.png')?no-repeat;?background-size:?auto?100%;}
.seven?{?background:url('images/QP7.png')?no-repeat;?background-size:?auto?100%;?}
.eight?{?background:url('images/QP8.png')?no-repeat;?background-size:?auto?100%;?}
.nine?{?background:url('images/QP9.png')?no-repeat;?background-size:?auto?100%;}
.ten{?background:url('images/QP10.png')?no-repeat;?background-size:?auto?100%;}
hi?test?it!
相關js代碼如下：var?getFlag=function?(id)?{
return?document.getElementById(id);???//獲取元素引用
}
var?extend=function(des,?src)?{
for?(p?in?src)?{
des[p]=src[p];
}
return?des;
}
var?clss=['one','two','three','four','five','six','seven','eight','nine','ten'];
var?Ball=function?(diameter,classn)?{
var?ball=document.createElement("div");
ball.className=classn;
with(ball.style)?{
width=height=diameter+'px';position='absolute';
}
return?ball;
}
var?Screen=function?(cid,config)?{
//先創建類的屬性
var?self=this;
if?(!(self?instanceof?Screen))?{
return?new?Screen(cid,config)
}
config=extend(Screen.Config,?config)????//configj是extend類的實例????self.container=getFlag(cid);????????????//窗口對象
self.container=getFlag(cid);
self.ballsnum=config.ballsnum;
self.diameter=80;???????????????????????//球的直徑
self.radius=self.diameter/2;
self.spring=config.spring;??????????????//球相碰后的反彈力
self.bounce=config.bounce;??????????????//球碰到窗口邊界后的反彈力
self.gravity=config.gravity;????????????//球的重力
self.balls=[];??????????????????????????//把創建的球置于該數組變量
self.timer=null;???????????????????????//調用函數產生的時間id
self.L_bound=0;???????????????????????//container的邊界
self.R_bound=self.container.clientWidth;??//document.documentElement.clientWidth?||?document.body.clientWidth?兼容性
self.T_bound=0;
self.B_bound=self.container.clientHeight;
};
Screen.Config={?????????????????????????//為屬性賦初值
ballsnum:10,
spring:0.8,
bounce:-0.9,
gravity:0.05
};
Screen.prototype={
initialize:function?()?{
var?self=this;
self.createBalls();
self.timer=setInterval(function?(){self.hitBalls()},?30)
},
createBalls:function?()?{
var?self=this,
num=self.ballsnum;
var?frag=document.createDocumentFragment();????//創建文檔碎片，避免多次刷新
for?(i=0;i
var?ball=new?Ball(self.diameter,clss[i]);
//var?ball=new?Ball(self.diameter,clss[?Math.floor(Math.random()*?num?)]);//這里是隨機的10個小球的碰撞效果
ball.diameter=self.diameter;
ball.radius=self.radius;
ball.style.left=(Math.random()*self.R_bound)+'px';??//球的初始位置，
ball.style.top=(Math.random()*self.B_bound)+'px';
ball.vx=Math.random()?*?6?-3;
ball.vy=Math.random()?*?6?-3;
frag.appendChild(ball);
self.balls[i]=ball;
}
self.container.appendChild(frag);
},
hitBalls:function?()?{
var?self=this,
num=self.ballsnum,
balls=self.balls;
for?(i=0;i
var?ball1=self.balls[i];
ball1.x=ball1.offsetLeft+ball1.radius;??????//小球圓心坐標
ball1.y=ball1.offsetTop+ball1.radius;
for?(j=i+1;j
var?ball2=self.balls[j];
ball2.x=ball2.offsetLeft+ball2.radius;
ball2.y=ball2.offsetTop+ball2.radius;
dx=ball2.x-ball1.x;??????????????????????//兩小球圓心距對應的兩條直角邊
dy=ball2.y-ball1.y;
var?dist=Math.sqrt(dx*dx?+?dy*dy);???????//兩直角邊求圓心距
var?misDist=ball1.radius+ball2.radius;???//圓心距最小值
if(dist?
//假設碰撞后球會按原方向繼續做一定的運動，將其定義為運動A
var?angle=Math.atan2(dy,dx);
//當剛好相碰，即dist=misDist時，tx=ballb.x,?ty=ballb.y
tx=ball1.x+Math.cos(angle)?*?misDist;
ty=ball1.y+Math.sin(angle)?*?misDist;
//產生運動A后，tx?>?ballb.x,?ty?>?ballb.y,所以用ax、ay記錄的是運動A的值
ax=(tx-ball2.x)?*?self.spring;
ay=(ty-ball2.y)?*?self.spring;
//一個球減去ax、ay，另一個加上它，則實現反彈
ball1.vx-=ax;
ball1.vy-=ay;
ball2.vx+=ax;
ball2.vy+=ay;
}
}
}
for?(i=0;i
self.moveBalls(balls[i]);
}
},
moveBalls:function?(ball)?{
var?self=this;
ball.vy+=self.gravity;
ball.style.left=(ball.offsetLeft+ball.vx)+'px';
ball.style.top=(ball.offsetTop+ball.vy)+'px';
//判斷球與窗口邊界相碰，把變量名簡化一下
var?L=self.L_bound,?R=self.R_bound,?T=self.T_bound,?B=self.B_bound,?BC=self.bounce;
if?(ball.offsetLeft?
ball.style.left=L;
ball.vx*=BC;
}
else?if?(ball.offsetLeft?+?ball.diameter?>?R)?{
ball.style.left=(R-ball.diameter)+'px';
ball.vx*=BC;
}
else?if?(ball.offsetTop?
ball.style.top=T;
ball.vy*=BC;
}
if?(ball.offsetTop?+?ball.diameter?>?B)?{
ball.style.top=(B-ball.diameter)+'px';
ball.vy*=BC;
}
}
}
window.οnlοad=function()?{
var?sc=null;
document.getElementById("inner").innerHTML='';
sc=new?Screen('inner',{ballsnum:10,?spring:0.3,?bounce:-0.9,?gravity:0.01});
sc.initialize();
getFlag('start').οnclick=function?()?{
document.getElementById("inner").innerHTML='';
sc=new?Screen('inner',{ballsnum:10,?spring:0.3,?bounce:-0.9,?gravity:0.01});
sc.initialize();
}
getFlag('stop').οnclick=function()?{
clearInterval(sc.timer);
}
}
看起來很簡單吧！
