html5清空画布方法（三种）

function clearCanvas<span style="font-family: Verdana, Arial, 宋体;">()</span>  
{  
    var c=document.getElementById("myCanvas");  
    var cxt=c.getContext("2d");  
    c.height=c.height;  
}  

function clearCanvas()  
{  
    var c=document.getElementById("myCanvas");  
    var cxt=c.getContext("2d");  
    cxt.clearRect(0,0,c.width,c.height);  
}  

function clearCanvas()  
{  
    var c=document.getElementById("myCanvas");  
    var cxt=c.getContext("2d");  
      
    cxt.fillStyle="#000000";  
    cxt.beginPath();  
    cxt.fillRect(0,0,c.width,c.height);  
    cxt.closePath();  
}