javascript实现与后端相同的枚举Enum对象

 1 ; 2 (function (global, undefined) { 3      4     global.Enum = function (namesToValues) { 5         var enumeration = function () { 6             throw "can't Instantiate Enumerations"; 7         }; 8         enumeration.setValue = function (x) { 9             var val = null;10             enumeration.foreach(function (i) {11                 if (i.value == x) {12                     val = enumeration[i.name];13                 }14             }, null);15             return val;16         };17 18         function inherit(superCtor) {19             var f = function () {20             };21             f.PRototype = superCtor;22             var ctor = function () {23             };24             ctor.prototype = new f();25             ctor.prototype.constructor = superCtor.constructor;26             return new ctor;27         }28 29         var proto = enumeration.prototype = {30             constructor: enumeration,31             toString: function () {32                 return this.name;33             },34             valueOf: function () {35                 return this.value;36             },37             toJSON: function () {38                 return this.name;39             }40         };41 42         enumeration.values = [];43 44         for (name in namesToValues) {45             var e = inherit(proto);46             e.name = name;47             e.value = namesToValues[name];48             enumeration[name] = e;49             enumeration.values.push(e);50 51         }52 53         enumeration.foreach = function (f, c) {54             for (var i = 0; i < this.values.length; i++) {55                 f.call(c, this.values[i]);56             }57         };58 59         return enumeration;60 61     };62 })(window);

var Qos = window.Enum({            AT_MOST_ONCE: 0,            AT_LEAST_ONCE: 1,            EXACTLY_ONCE: 2,            DEFAULT: 3        });

现在我们打印Qos.AT_MOST_ONCE会现实一个对象，但是当我们进行Qos.AT_MOST_ONCE==1 比较时为true；而且Qos.setValue(1) 与Qos.AT_MOST_ONCE相同

Qos.AT_MOST_ONCE.toString() -> 'AT_MOST_ONCE' ;Qos.AT_MOST_ONCE.valueOf() -> 1 ; Qos.AT_MOST_ONCE.name -> 'AT_MOST_ONCE' ; Qos.AT_MOST_ONCE.value -> 1;

好，现在一个特点与后端语言特性相同的Enum对象就此出现了！！！