JavaScript dragging, collision, gravity and elastic movement example analysis_javascript skills

The examples in this article describe the implementation methods of JavaScript drag, collision, gravity and elastic movement. Share it with everyone for your reference, the details are as follows:

js drag, collision and gravity implementation code:

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 elastic motion implementation code:

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);
}

For more content related to JavaScript motion effects, please view the special topic on this site: " Summary of JavaScript motion effects and techniques"

I hope this article will be helpful to everyone in JavaScript programming.