以下内容是否会使对象满足枚举在JavaScript中的所有特性？类似于：
my.namespace.ColorEnum = {
RED : 0,
GREEN : 1,
BLUE : 2
}
// later on
if(currentColor == my.namespace.ColorEnum.RED) {
// whatever
}
还是有其他方法可以做到这一点？
当前回答
我认为它很容易使用。https://stackoverflow.com/a/32245370/4365315
var A = {a:11, b:22},
enumA = new TypeHelper(A);
if(enumA.Value === A.b || enumA.Key === "a"){
...
}
var keys = enumA.getAsList();//[object, object]
//set
enumA.setType(22, false);//setType(val, isKey)
enumA.setType("a", true);
enumA.setTypeByIndex(1);
更新：
这是我的助手代码（TypeHelper）。
var助手={isEmpty：函数（obj）{回来obj | | obj===null | | obj===未定义| | Array.isArray（obj）&&obj.length===0；},isObject：函数（obj）{return（对象类型==“object”）；},sortObjectKeys:函数（对象）{return Object.keys（对象）.sort（函数（a，b）{c=a-b；返回c});},containsItem:函数（arr，item）{if（arr&&Array.isArray（arr））{return arr.indexOf（项）>-1；}其他{返回arr==项；}},pushArray：函数（arr1，arr2）{if（arr1&&arr2&&Array.isArray（arr1））{arr1.push.apply（arr1，Array.isArray（arr2）？arr2:[arr2]）；}}};函数TypeHelper（）{var_types=参数[0]，_defTypeIndex＝0，_电流类型，_值，_allKeys=助手.sortObjectKeys（_types）；if（arguments.length==2）{_defTypeIndex=参数[1]；}对象定义属性（this{关键字：{get:函数（）{return _currentType；},集合：函数（val）{_currentType.setType（val，true）；},可枚举：真},值：{get:函数（）{返回类型[_currentType]；},集合：函数（val）{_value.setType（val，false）；},可枚举：真}});this.getAsList=函数（键）{var列表=[]；_allKeys.forEach（函数（键、idx、数组）{if（键和类型[key]）{if（！Helper.isEmpty（keys）&&Helper.containsItem（keys，key）|| Helper.isEmpty（key））{var json=｛｝；json.Key=密钥；json.Value=_types[key]；Helper.pushArray（列表，json）；}}});返回列表；};this.setType=函数（值，isKey）{if（！Helper.isEmpty（value））{Object.keys（_types）.forEach（函数（key，idx，array）{if（Helper.isObject（值））{if（value&&value.Key==Key）{_currentType=键；}}else if（isKey）{if（value&&value.toString（）==key.toString（））{_currentType=键；}}否则如果（value&&value.toString（）==_types[key]）{_currentType=键；}});}其他{this.setDefaultType（）；}return isKey_类型[_currentType]：_currentType；};this.setTypeByIndex=函数（索引）{对于（变量i=0；i<_allKeys.length；i++）{如果（索引==i）{_currentType=_allKeys[index]；打破}}};this.setDefaultType=函数（）{this.setTypeByIndex（_defTypeIndex）；};this.setDefaultType（）；}变量类型A={“-1”：“任意”，“2”：“2L”，“100”：“100L”，“200”：“200L”，“1000”：“1000升”};var enumA=新的TypeHelper（TypeA，4）；document.writeln（“Key=”，enumA.Key，”，Value=“，enumA.Value，”<br>“）；enumA.setType（“200L”，假）；document.writeln（“Key=”，enumA.Key，”，Value=“，enumA.Value，”<br>“）；enumA.setDefaultType（）；document.writeln（“Key=”，enumA.Key，”，Value=“，enumA.Value，”<br>“）；enumA.setTypeByIndex（1）；document.writeln（“Key=”，enumA.Key，”，Value=“，enumA.Value，”<br>“）；document.writeln（“等于=”，（enumA.Value==TypeA[“2”]））；
其他回答
var DaysEnum = Object.freeze ({ monday: {}, tuesday: {}, ... });
您不需要指定id，只需使用空对象来比较枚举即可。
if (incommingEnum === DaysEnum.monday) //incommingEnum is monday
EDIT：如果要序列化对象（例如JSON），将再次输入id。
（摘自加布里埃尔·利亚马斯评论）（根据Stijn de Witt的评论进行编辑）
我提出了一种以Java中的枚举为模型的方法。这些是类型安全的，因此您也可以执行instanceof检查。
可以这样定义枚举：
var Days = Enum.define("Days", ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"]);
Days现在引用Days枚举：
Days.Monday instanceof Days; // true
Days.Friday.name(); // "Friday"
Days.Friday.ordinal(); // 4
Days.Sunday === Days.Sunday; // true
Days.Sunday === Days.Friday; // false
Days.Sunday.toString(); // "Sunday"
Days.toString() // "Days { Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday } "
Days.values().map(function(e) { return e.name(); }); //["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"]
Days.values()[4].name(); //"Friday"
Days.fromName("Thursday") === Days.Thursday // true
Days.fromName("Wednesday").name() // "Wednesday"
Days.Friday.fromName("Saturday").name() // "Saturday"
实施：
var Enum = (function () {
/**
* Function to define an enum
* @param typeName - The name of the enum.
* @param constants - The constants on the enum. Can be an array of strings, or an object where each key is an enum
* constant, and the values are objects that describe attributes that can be attached to the associated constant.
*/
function define(typeName, constants) {
/** Check Arguments **/
if (typeof typeName === "undefined") {
throw new TypeError("A name is required.");
}
if (!(constants instanceof Array) && (Object.getPrototypeOf(constants) !== Object.prototype)) {
throw new TypeError("The constants parameter must either be an array or an object.");
} else if ((constants instanceof Array) && constants.length === 0) {
throw new TypeError("Need to provide at least one constant.");
} else if ((constants instanceof Array) && !constants.reduce(function (isString, element) {
return isString && (typeof element === "string");
}, true)) {
throw new TypeError("One or more elements in the constant array is not a string.");
} else if (Object.getPrototypeOf(constants) === Object.prototype && !Object.keys(constants).reduce(function (isObject, constant) {
return Object.getPrototypeOf(constants[constant]) === Object.prototype;
}, true)) {
throw new TypeError("One or more constants do not have an associated object-value.");
}
var isArray = (constants instanceof Array);
var isObject = !isArray;
/** Private sentinel-object used to guard enum constructor so that no one else can create enum instances **/
function __() { };
/** Dynamically define a function with the same name as the enum we want to define. **/
var __enum = new Function(["__"],
"return function " + typeName + "(sentinel, name, ordinal) {" +
"if(!(sentinel instanceof __)) {" +
"throw new TypeError(\"Cannot instantiate an instance of " + typeName + ".\");" +
"}" +
"this.__name = name;" +
"this.__ordinal = ordinal;" +
"}"
)(__);
/** Private objects used to maintain enum instances for values(), and to look up enum instances for fromName() **/
var __values = [];
var __dict = {};
/** Attach values() and fromName() methods to the class itself (kind of like static methods). **/
Object.defineProperty(__enum, "values", {
value: function () {
return __values;
}
});
Object.defineProperty(__enum, "fromName", {
value: function (name) {
var __constant = __dict[name]
if (__constant) {
return __constant;
} else {
throw new TypeError(typeName + " does not have a constant with name " + name + ".");
}
}
});
/**
* The following methods are available to all instances of the enum. values() and fromName() need to be
* available to each constant, and so we will attach them on the prototype. But really, they're just
* aliases to their counterparts on the prototype.
*/
Object.defineProperty(__enum.prototype, "values", {
value: __enum.values
});
Object.defineProperty(__enum.prototype, "fromName", {
value: __enum.fromName
});
Object.defineProperty(__enum.prototype, "name", {
value: function () {
return this.__name;
}
});
Object.defineProperty(__enum.prototype, "ordinal", {
value: function () {
return this.__ordinal;
}
});
Object.defineProperty(__enum.prototype, "valueOf", {
value: function () {
return this.__name;
}
});
Object.defineProperty(__enum.prototype, "toString", {
value: function () {
return this.__name;
}
});
/**
* If constants was an array, we can the element values directly. Otherwise, we will have to use the keys
* from the constants object.
*/
var _constants = constants;
if (isObject) {
_constants = Object.keys(constants);
}
/** Iterate over all constants, create an instance of our enum for each one, and attach it to the enum type **/
_constants.forEach(function (name, ordinal) {
// Create an instance of the enum
var __constant = new __enum(new __(), name, ordinal);
// If constants was an object, we want to attach the provided attributes to the instance.
if (isObject) {
Object.keys(constants[name]).forEach(function (attr) {
Object.defineProperty(__constant, attr, {
value: constants[name][attr]
});
});
}
// Freeze the instance so that it cannot be modified.
Object.freeze(__constant);
// Attach the instance using the provided name to the enum type itself.
Object.defineProperty(__enum, name, {
value: __constant
});
// Update our private objects
__values.push(__constant);
__dict[name] = __constant;
});
/** Define a friendly toString method for the enum **/
var string = typeName + " { " + __enum.values().map(function (c) {
return c.name();
}).join(", ") + " } ";
Object.defineProperty(__enum, "toString", {
value: function () {
return string;
}
});
/** Freeze our private objects **/
Object.freeze(__values);
Object.freeze(__dict);
/** Freeze the prototype on the enum and the enum itself **/
Object.freeze(__enum.prototype);
Object.freeze(__enum);
/** Return the enum **/
return __enum;
}
return {
define: define
}
})();
我一直在摆弄这个，因为我喜欢我的遗珠
使用Object.defineProperty，我想我找到了一个可行的解决方案。
这里有一个jsfiddle：http://jsfiddle.net/ZV4A6/
使用此方法。。理论上，您应该能够为任何对象调用和定义枚举值，而不会影响该对象的其他属性。
Object.defineProperty(Object.prototype,'Enum', {
value: function() {
for(i in arguments) {
Object.defineProperty(this,arguments[i], {
value:parseInt(i),
writable:false,
enumerable:true,
configurable:true
});
}
return this;
},
writable:false,
enumerable:false,
configurable:false
});
由于属性可写：false，这应该使其类型安全。
因此，您应该能够创建一个自定义对象，然后对其调用Enum（）。分配的值从0开始，每项递增。
var EnumColors={};
EnumColors.Enum('RED','BLUE','GREEN','YELLOW');
EnumColors.RED; // == 0
EnumColors.BLUE; // == 1
EnumColors.GREEN; // == 2
EnumColors.YELLOW; // == 3
这是Typescript将其枚举转换为Javascript的方式：
var makeEnum = function(obj) {
obj[ obj['Active'] = 1 ] = 'Active';
obj[ obj['Closed'] = 2 ] = 'Closed';
obj[ obj['Deleted'] = 3 ] = 'Deleted';
}
Now:
makeEnum( NewObj = {} )
// => {1: "Active", 2: "Closed", 3: "Deleted", Active: 1, Closed: 2, Deleted: 3}
起初我很困惑obj[1]为什么返回“Active”，但后来意识到它的死简单赋值运算符赋值，然后返回：
obj['foo'] = 1
// => 1
底线：你不能。
你可以伪造它，但你不会得到类型安全。通常，这是通过创建映射到整数值的字符串值的简单字典来完成的。例如：
var DaysEnum = {"monday":1, "tuesday":2, "wednesday":3, ...}
Document.Write("Enumerant: " + DaysEnum.tuesday);
这种方法有什么问题？您可能会意外地重新定义枚举，或者意外地具有重复的枚举值。例如：
DaysEnum.monday = 4; // whoops, monday is now thursday, too
编辑
Artur Czajka的Object.freeze呢？这难道不会阻止你将星期一设置为星期四吗油炸四方饼
当然，Object.freeze可以完全解决我投诉的问题。我想提醒大家，当我写上述内容时，Object.freeze并不存在。
现在现在它打开了一些非常有趣的可能性。
编辑2这里有一个非常好的用于创建枚举的库。
http://www.2ality.com/2011/10/enums.html
虽然它可能不适合枚举的每一种有效使用，但它需要很长的路。
