js拖拽、碰撞与重力实现代码：
window.onload=function () { var oDiv=document.getElementById('div1'); var lastX=0; var lastY=0; oDiv.onmousedown=function (ev) { var oEvent=ev||event; var disX=oEvent.clientX-oDiv.offsetLeft; var disY=oEvent.clientY-oDiv.offsetTop; document.onmousemove=function (ev) { var oEvent=ev||event; var l=oEvent.clientX-disX; var t=oEvent.clientY-disY; oDiv.style.left=l+'px'; oDiv.style.top=t+'px'; iSpeedX=l-lastX; iSpeedY=t-lastY; lastX=l; lastY=t; document.title='x:'+iSpeedX+', y:'+iSpeedY; }; document.onmouseup=function () { document.onmousemove=null; document.onmouseup=null; startMove(); }; clearInterval(timer); }; }; var timer=null; var iSpeedX=0; var iSpeedY=0; function startMove() { clearInterval(timer); timer=setInterval(function (){ var oDiv=document.getElementById('div1'); iSpeedY+=3; var l=oDiv.offsetLeft+iSpeedX; var t=oDiv.offsetTop+iSpeedY; if(t>=document.documentElement.clientHeight-oDiv.offsetHeight) { iSpeedY*=-0.8; iSpeedX*=0.8; t=document.documentElement.clientHeight-oDiv.offsetHeight; } else if(t<=0) { iSpeedY*=-1; iSpeedX*=0.8; t=0; } if(l>=document.documentElement.clientWidth-oDiv.offsetWidth) { iSpeedX*=-0.8; l=document.documentElement.clientWidth-oDiv.offsetWidth; } else if(l<=0) { iSpeedX*=-0.8; l=0; } if(Math.abs(iSpeedX)<1) { iSpeedX=0; } if(Math.abs(iSpeedY)<1) { iSpeedY=0; } if(iSpeedX==0 && iSpeedY==0 && t==document.documentElement.clientHeight-oDiv.offsetHeight) { clearInterval(timer); alert('停止'); } else { oDiv.style.left=l+'px'; oDiv.style.top=t+'px'; } document.title=iSpeedX; }, 30); }
js弹性运动实现代码：
var left=0; //用left变量存储赋给obj.style.left的值，以防每次系统都省略小数，所导致最后结果的细微差异 var iSpeed=0; function startMove(obj,iTarget) { clearInterval(obj.timer); obj.timer=setInterval(function(){ iSpeed+=(iTarget-obj.offsetLeft)/5; //速度 iSpeed*=0.7; //考虑阻力 left+=iSpeed; if(Math.abs(iSpeed)<1&&Math.abs(iTarget-obj.offsetLeft)<1) //停止条件 速度和距离绝对值小于1 { clearInterval(obj.timer); obj.style.left=iTarget+"px"; //清楚后，顺便把目标值赋给obj.style.left } else { obj.style.left=left+"px"; } },30); }