简单的jquery对 密码 框的密码进行 混淆

 /**
  * 密码混淆器
  */
  $.fn.enKey = function(size){
   var size = (size === undefined || isNaN(size)) ? 4 : size;
   var self = this;
   this.keyup(function(event){
    var charAll = "0123456789abcdefghijklmnop"+
     "qrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    var changValue = function(value){
     var charResult = "";
     var charArray = charAll.split("");
     var charLen = charArray.length;
     for(var i = 0 ; i < size ; i++){
      var randValue = Math.floor(Math.random()*charLen);
      charResult += charAll[randValue];
     }
     return (charResult);
    }
    if(    (65<=event.keyCode && event.keyCode<=90) ||
     (48<=event.keyCode && event.keyCode<=57) ||
     (96<=event.keyCode && event.keyCode<=105)){
     self.val(self.val()+changValue(event.keyCode));
    }
   })
  }
 
 
 
  $("input[name='password']").enKey(2);