javascript 实现自由落体的方块效果


答案：你可以试着按下鼠标左键，然后拖拽出一个方块后释放，看效果 
<!DOCTYPE html public "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> 
<title>Simple xhtml page</title> 
<style> 
div.container{ 
position:absolute; 
border:1px solid #333; 
font-size:0px; 
filter: alpha(opacity=60); 
opacity: 0.6; 
} 
</style> 
</head> 
<body> 
<script type="text/javascript"> 
<!-- 
function Draw(event){ 
this.mouseDownEvent = event||window.event; 
this.node = null; 
this.pointX = null; 
this.pointY = null; 
this.dropCount = 0; 
this.dropId = null; 
this.fadeCount = 0; 
this.fadeId = null; 
} 

Draw.prototype.colors = ["#CCFF99","#FF9966","#CC0000","#00FF00","#330000","#00CC00","#339900","#660066","#CC66FF","#FF00FF","#CC0000","#993300","#006600","#3300FF","#0000CC","#663300","#66CCFF","#33FF66","#669900"]; 

Draw.prototype.randomColor = function(){ 
return this.colors[Math.floor(Math.random()*this.colors.length)]; 
} 

Draw.prototype.createDiv = function(){ 
var e = this.mouseDownEvent; 
var div = document.createElement("div"); 
div.className="container"; 
div.style.top = e.clientY + "px"; 
div.style.left = e.clientX + "px"; 
div.style.backgroundColor = this.randomColor(); 
document.body.appendChild(div); 
this.node = div; 
this.pointX = e.clientX; 
this.pointY = e.clientY; 
} 

Draw.prototype.resizeDiv = function(e){ 
e = e || window.event; 
var self = this; 
self.node.style.width = Math.abs(e.clientX-self.pointX)+"px"; 
self.node.style.height = Math.abs(e.clientY-self.pointY)+"px"; 
self.node.style.left = Math.min(self.pointX, e.clientX)+"px"; 
self.node.style.top = Math.min(self.pointY, e.clientY)+"px"; 
} 

Draw.prototype.drop = function(){ 
var self = this; 
self.dropId = window.setInterval(function(){ 
var dc = document.documentElement.clientHeight; 
var dh = self.node.offsetHeight; 
var dt = self.node.offsetTop; 
if(dt>=dc-dh){clearInterval(self.dropId);self.fade();} 
self.node.style.top = Math.min(dt+(++self.dropCount*2-1)*5, dc-dh)+"px"; 
},50); 
} 

Draw.prototype.fade = function(){ 
var self = this; 
self.node.style.backgroundColor = self.randomColor(); 
self.node.style.filter = "alpha(opacity=100)"; 
self.node.style.opacity = 1; 
self.fadeId = window.setInterval(function(){ 
if(++self.fadeCount>100){clearInterval(self.fadeId);} 
self.node.style.filter = "alpha(opacity="+(100-self.fadeCount)+")"; 
self.node.style.opacity = (100-self.fadeCount)/100; 
},10); 
} 

document.onmousedown = function(event){ 
var drawObject = new Draw(event); 
drawObject.createDiv(); 
document.onmousemove = function(event){ 
drawObject.resizeDiv(event); 
} 
document.onmouseup = function(){ 
document.onmousemove = null; 
window.setTimeout(function(){drawObject.drop()}, 1000); 
} 
} 
//--> 
</script> 
</body> 
</html>

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