js之padLeft

pad1:

function pad(num, n) {
  return (Math.pow(10,n)+num+'').substr(1);  //缺点：位数长度有限，15位以内。
}
alert(pad(3,6)); 

pad2:

function pad(num, n) {
   y='00000000000000000000000000000'+num; //爱几个0就几个，自己够用就行
   return y.substr(y.length-n);
}
alert(pad(3,6));

pad3:

String.prototype.padLeft=function(len,ch){
    ch=typeof(ch)==='undefined'?' ':ch;
    var s=String(this);
    while(s.length<len)
        s=ch+s;
    return s;
}

From : http://topic.csdn.net/u/20100421/16/817ef7c6-6675-49e1-bf39-b4a96c08b41e.html?13969
More : http://www.cnblogs.com/bluedream2009/archive/2009/09/08/1562910.html