javascript实现与后端相同的枚举Enum对象

 ;
 (function (global, undefined) {

     global.Enum = function (namesToValues) {
         var enumeration = function () {
             throw "can't Instantiate Enumerations";
         };
         enumeration.setValue = function (x) {
             var val = null;
             enumeration.foreach(function (i) {
                 if (i.value == x) {
                     val = enumeration[i.name];
                 }
             }, null);
             return val;
         };

         function inherit(superCtor) {
             var f = function () {
             };
             f.prototype = superCtor;
             var ctor = function () {
             };
             ctor.prototype = new f();
             ctor.prototype.constructor = superCtor.constructor;
             return new ctor;
         }

         var proto = enumeration.prototype = {
             constructor: enumeration,
             toString: function () {
                 return this.name;
             },
             valueOf: function () {
                 return this.value;
             },
             toJSON: function () {
                 return this.name;
             }
         };

         enumeration.values = [];

         for (name in namesToValues) {
             var e = inherit(proto);
             e.name = name;
             e.value = namesToValues[name];
             enumeration[name] = e;
             enumeration.values.push(e);

         }

         enumeration.foreach = function (f, c) {
             for (var i = 0; i < this.values.length; i++) {
                 f.call(c, this.values[i]);
             }
         };

         return enumeration;

     };
 })(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！！！