解决XML中< > ' " & 特殊字符问题

 function  encode(v)
    {
        if(v == null||v=="")
            return "";
		var result="";
        for(var i = 0; i < v.length; i++)
            switch(v.charAt(i))
            {
            case "<": result+="&lt;";break;
            case ">": result+="&gt;"; break;
            case "&":result+="&amp;";break;
            case "\"": result+="&quot;";break;
            case "'": result+="&#39;";break;
            default:result+=v.charAt(i);break;
            }
        return result;
	}