js正則練習問題

var str = "839243680";
    var ary = [" "," "," "," "," "," "," "," "," "," "];
    str = str.replace(/\d/g,function(){
        return ary[arguments[0]];
    });
    console.log(str);  // -->          

   ：
if(!String.prototype.trim){
        String.prototype.trim = function () {
            return this.replace(/(^\s*)|(\s*$)/g, "");
        };
}
   ：
function myTrim(str){
        if(typeof trim == "function"){
            return str.trim();
        }else{
            return str.replace(/(^\s*)|(\s*$)/g, "");
        }
    }