javascript模拟枚举的简单实例

如下，我们来定义Week的枚举：

if(typeof WeekDay == "undefined"){ 
var WeekDay = {};
WeekDay.Sunday = 0;
WeekDay.Monday = 1;
WeekDay.Tuesday = 2;
WeekDay.Wedesay = 3;
WeekDay.Thursday = 4;
WeekDay.Friday = 5;
WeekDay.Saturday = 6;
}

当然，我们有更为直观的方式。以定义DOM文档节点类型为例，定义方式如下：

if(typeof Node == "undefined"){ 
var Node = {
ELEMENT_NODE: 1,
ATTRIBUTE_NODE: 2,
TEXT_NODE: 3,
CDATA_SECTION_NODE: 4,
ENTITY_REFERENCE_NODE: 5,
ENTITY_NODE: 6,
PROCESSING_INSTRUCTION_NODE: 7,
COMMENT_NODE: 8,
DOCUMENT_NODE: 9,
DOCUMENT_TYPE_NODE: 10,
DOCUMENT_FRAGEMENT_NODE: 11,
NOTATION_NODE: 12
}
}

alert(document.nodeType == Node.DOCUMENT_NODE);  // -----> Output: true

与类C语言类似，以上2个例子的枚举对应属性值均为整形。你可能想到，难道还能定义成别的类型？要回答这个问题，得先知道咱们这个枚举实现的原理。前面说到，这里是用JSON来实现的，而JSON可以使用任何类型的值！所以，Js中的枚举可以是任何类型的值。以下以String类型为例：

if(typeof Color == "undefined"){ 
var Color = { 
Color1: 'red', 
Color2: 'green', 
Color3: 'white', 
Color4: 'black' 
} 
}

以更为复杂的类型来定义一个PersonList枚举如下：

if(typeof PersonList == "undefined"){ 
var PersonList = {
ZhangSan: {
Id: 1,
Name: 'ZhangSan',
Gender: 'man'
},
LiSi: {
Id: 2,
Name: 'LiSi',
Gender: 'woman'
},
ZhaoWu: {
Id: 3,
Name: 'ZhaoWu',
Gender: 'man'
}
}
}