freedown.js

综合JavaScript和CSS实现一个小球的自由落体运动

// JavaScript Document
var time=0.1;
function freedown(){
	if(!document.getElementById) 
	return false;
	if(!document.getElementById("image"))
	return false;
	var elem=document.getElementById("image");
	var xpos=parseInt(elem.style.left);
	var ypos=parseInt(elem.style.top);
	
	if(xpos==50 && ypos==500){
		return true;
	}
	if(ypos<500){
		ypos=50+5*time*time;
		time=time+0.1;
		//unit of time is second ,100ms display once
	}
	elem.style.left=xpos+"px";
	elem.style.top=ypos+"px";
	movement = setTimeout("freedown()",50);
}