js中的string.format

String.prototype.format = function(args) {
            var result = this;
            if (arguments.length > 0) {
                if (arguments.length == 1 && typeof (args) == "object") {
                    for (var key in args) {
                        if (args[key] != undefined) {
                            var reg = new RegExp("({" + key + "})", "g");
                            result = result.replace(reg, args[key]);
                        }
                    }
                }
                else {
                    for (var i = 0; i < arguments.length; i++) {
                        if (arguments[i] != undefined) {
                            //var reg = new RegExp("({[" + i + "]})", "g");//这个在索引大于9时会有问题，谢谢何以笙箫的指出
                            var reg = new RegExp("({)" + i + "(})", "g");
                            result = result.replace(reg, arguments[i]);
                        }
                    }
                }
            }
            return result;
        }
        String.format = function () {
            if (arguments.length == 0)
                return null;

            var str = arguments[0];
            for (var i = 1; i < arguments.length; i++) {
                var re = new RegExp('\\{' + (i - 1) + '\\}', 'gm');
                str = str.replace(re, arguments[i]);
            }
            return str;
        }

//两种调用方式
 var template1="我是{0}，今年{1}了";
 var template2="我是{name}，今年{age}了";
 var result1=template1.format("loogn",22);
 var result2=template2.format({name:"loogn",age:22});

//两个结果都是"我是loogn，今年22了"

var a = "I Love {0}, and You Love {1},Where are {0}! {4}";
alert(String.format(a, "You","Me"));

alert(a.format("You","Me"));