HTML5网页Loading加载效果

答案：<!doctype html>  
    <html>  
      <head>  
        <meta http-equiv="content-type" content="GBK"/>  
        <title>HTML5-loading</title>  
        <script type="text/javascript">  
        function loading(canvas,options){   
          this.canvas = canvas;   
          if(options){   
            this.radius = options.radius||12;   
            this.circleLineWidth = options.circleLineWidth||4;   
            this.circleColor = options.circleColor||'lightgray';   
            this.dotColor = options.dotColor||'gray';   
          }else{         
            this.radius = 12;   
            this.circelLineWidth = 4;   
            this.circleColor = 'lightgray';   
            this.dotColor = 'gray';   
          }   
        }   
        loading.prototype = {   
          show:function (){   
            var canvas = this.canvas;   
            if(!canvas.getContext)return;   
            if(canvas.__loading)return;   
            canvas.__loading = this;   
            var ctx = canvas.getContext('2d');   
            var radius = this.radius;         
            var rotators = [{angle:0,radius:1.5},{angle:3/radius,radius:2},{angle:7/radius,radius:2.5},{angle:12/radius,radius:3}];         
            var me = this;   
            canvas.loadingInterval = setInterval(function(){   
              ctx.clearRect(0,0,canvas.width,canvas.height);            
              var lineWidth = me.circleLineWidth;   
              var center = {x:canvas.width/2 - radius,y:canvas.height/2-radius};             
              ctx.beginPath();   
              ctx.lineWidth = lineWidth;   
              ctx.strokeStyle = me.circleColor;   
              ctx.arc(center.x,center.y,radius,0,Math.PI*2);   
              ctx.closePath();   
              ctx.stroke();   
              for(var i=0;i<rotators.length;i++){           
                var rotatorAngle = rotators[i].currentAngle||rotators[i].angle;               
                //在圆圈上面画小圆   
       var rotatorCenter = {x:center.x-(radius)*Math.cos(rotatorAngle) ,y:center.y-(radius)*Math.sin(rotatorAngle)};               
                var rotatorRadius = rotators[i].radius;   
                ctx.beginPath();   
                ctx.fillStyle = me.dotColor;   
                ctx.arc(rotatorCenter.x,rotatorCenter.y,rotatorRadius,0,Math.PI*2);   
                ctx.closePath();   
                ctx.fill();   
                rotators[i].currentAngle = rotatorAngle+4/radius;   
              }   
            },50);   
          },   
          hide:function(){   
            var canvas = this.canvas;   
            canvas.__loading = false;   
            if(canvas.loadingInterval){   
              window.clearInterval(canvas.loadingInterval);   
            }   
            var ctx = canvas.getContext('2d');   
            if(ctx)ctx.clearRect(0,0,canvas.width,canvas.height);   
          }   
        };   
        </script>  
      </head>  
      <body>  
        <canvas id="canvas" width="300" height="100" style="border:1px solid #69c"></canvas>  
        <p>  
        <input type="button" onclick="loadingObj.hide()" value="HideLoading"/>  
        <input type="button" onclick="loadingObj.show()" value="showLoading"/>  
        </p>  
        <script>  
        var loadingObj = new loading(document.getElementById('canvas'),{radius:8,circleLineWidth:3});   
        loadingObj.show();   
        </script>  
      </body>  
    </html>
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