碰撞运动js

window.onload=function(){

var oCrash=document.getElementById('crash');

var speedX=5;

var speedY=5;

startCrash();

function startCrash(){

setInterval(function(){

var X=oCrash.offsetLeft+speedX;

var Y=oCrash.offsetTop+speedY;

if(X > document.documentElement.clientWidth - oCrash.offsetWidth){

X=document.documentElement.clientWidth-oCrash.offsetWidth;

speedX*=-1;

}else if(X < 0){

X=0;

speedX*=-1;

}

if(Y > document.documentElement.clientHeight-oCrash.offsetHeight){

Y=document.documentElement.clientHeight-oCrash.offsetHeight;

speedY*=-1;

}else if(Y < 0){

Y=0;

speedY*=-1;

}

oCrash.style.left = X + 'px';

oCrash.style.top = Y + 'px';

},35);

}

}