TypeScript枚举-编程知识

1、数字枚举

enum Direction {Up,Down,Left,Right,
}

var Direction;
(function (Direction) {Direction[Direction["Up"] = 0] = "Up";Direction[Direction["Down"] = 1] = "Down";Direction[Direction["Left"] = 2] = "Left";Direction[Direction["Right"] = 3] = "Right";
})(Direction || (Direction = {}));

可以反向映射

enum AnimalFlags {None = 0,HasClaws = 1  << 0,CanFly = 1 << 1
}interface Animal {flags: AnimalFlags;[key: string]: any
}function printAnimalAbilities(animal: Animal) {var animalFlags = animal.flags;if(animalFlags & AnimalFlags.HasClaws) {console.log('animal has claws')}if(animalFlags & AnimalFlags.CanFly) {console.log('animal has fly')}if(animalFlags == AnimalFlags.None) {console.log('nothing')}
}var animal = { flags: AnimalFlags.None };
printAnimalAblities(animal); // 什么都没有
animal.flags |= AnimalFlags.HasClaws;
printAnimalAblities(animal); // 动物有爪子
animal.flags &= ~AnimalFlags.HasClaws;
printAnimalAblities(animal); // 什么都没有
animal.flags |= AnimalFlags.HasClaws | AnimalFlags.CanFly;
printAnimalAblities(animal); // 动物有爪子，能飞翔

在这里，我们可以进行如下操作。

使用 |= 来添加一个标记。
组合使用&= 和 ~ 来清理一个标记。
使用 | 来合并标记。

1.1 数字枚举和数字类型

TypeScript的枚举是基于数字的，这意味着可以将数字类型赋值给枚举类型的实例

enum Color {Red,Green,Blue
}
let col = Color.Red;
col = 0; // 与Color.Red一样有效

2、字符串枚举

enum Direction {Up = "上",Down = "下",Left = "左",Right = "右"
}

var Direction;
(function (Direction) {Direction["Up"] = "\u4E0A";Direction["Down"] = "\u4E0B";Direction["Left"] = "\u5DE6";Direction["Right"] = "\u53F3";
})(Direction || (Direction = {}));

3、异构枚举

enum Direction {Up,Down = "下",Left = "左",Right = "右"
}

var Direction;
(function (Direction) {Direction[Direction["Up"] = 0] = "Up";Direction["Down"] = "\u4E0B";Direction["Left"] = "\u5DE6";Direction["Right"] = "\u53F3";
})(Direction || (Direction = {}));

4、枚举成员

enum Char {//const a,b = 1 + 3,c = Char.a,//computedd = Math.random(),e = "123".length
}

var Char;
(function (Char) {//const Char[Char["a"] = 0] = "a";Char[Char["b"] = 4] = "b";Char[Char["c"] = 0] = "c";//computedChar[Char["d"] = Math.random()] = "d";Char[Char["e"] = "123".length] = "e";
})(Char || (Char = {}));

5、常量枚举

在编译阶段被移除（提高性能）

const enum Month {Jan,Feb,Mar
}

编译：

const enum Month {Jan,Feb,Mar
}
let month = [Month.Jan,Month.Feb,Month.Mar]

编译：

var month = [0 /* Jan */, 1 /* Feb */, 2 /* Mar */];

const enum Title {False,True,Unkonown
}
const title: Title = Title.False

通过设置--preserveConstEnums，运行时可以使用保留编译后的变量

var Title;
(function (Title) {Title[Title["False"] = 0] = "False";Title[Title["True"] = 1] = "True";Title[Title["Unknown"] = 2] = "Unknown";
})(Title || (Title = {}));
var title = 0 /* False */;

6、有静态方法的枚举

使用enum + namespace的声明方式向枚举类型添加静态方法。我们将静态成员isBusinessDay添加到枚举上。

enum Weekday {Monday,Tuesday,Wednesday,Tuseday,Friday,Saturday,Sunday
}namespace Weekday {export function isBusinessDay(day:Weekday) {switch(day) {case Weekday.Saturday:case Weekday.Sunday:return false;default true;}}
}
const mon = Weekday.Monday;
const sun = Weekday.Sunday;console.log(Weekday.isBusinessDay(mon)) //true
console.log(Weekday.isBusinessDay(sun)) //false

7、示例

7.1、创建数组

interface MapItem<TEnum, CnEnum> {key: string,value: string,label: string
}
/*** @description: 将 enum 与中文 enum 转换为数组，适合直接输出在 v-for 里* @param {TEnum} map* @param {CnEnum} mapCn* @return {MapItem[]} 返回适合于循环的数组*    key：enum 大写的 key*    value：传给后端的值*    label：中文值*/
export function convertMap<TEnum, CnEnum>(map: TEnum, mapCn: CnEnum):MapItem<TEnum, CnEnum>[] {return Object.keys(mapCn).map(key => {return {key,value: map[key],label: mapCn[key]}})
}interface ValueLabel {[key: string]: string
/*** @description: 返回后端的值对应中文的对象* @param {TEnum} map* @param {CnEnum} mapCn* @return {ValueLabel} 后端的值对应中文，例如{ Y: 是, N: 否 }*/
}
export function convertValueLabel<TEnum, CnEnum>(map: TEnum, mapCn: CnEnum): ValueLabel {const valueLabel:ValueLabel = {}Object.keys(mapCn).forEach(key => {valueLabel[map[key]] = mapCn[key]})return valueLabel
}/*** @description: 同上，只不过是中文对应英文* @param {TEnum} map* @param {CnEnum} mapCn* @return {ValueLabel} 中文对应后端的值，例如{ 是: Y, 否: N }*/
export function convertLabelValue<TEnum, CnEnum>(map: TEnum, mapCn: CnEnum): ValueLabel {const valueLabel:ValueLabel = {}Object.keys(mapCn).forEach(key => {valueLabel[mapCn[key]] = map[key]})return valueLabel
}

7.2、Map

enum E {a,b}
enum F {a = 0, b=1 }
enum G {a='apple',b ='banana'}let e: E = 3
let f: F = 3
e === f // errorlet e1: E.a = 1
let e2: E.b = 1
let e3: E.a = 1
e1 === e3 // true
e1 === e2 // false

7.3、Map

export enum sizeEnum {XS = 'XS',SM = 'SM',MD = 'MD',LG = 'LG',XL = 'XL',XXL = 'XXL',
}export enum screenEnum {XS = 480,SM = 576,MD = 768,LG = 992,XL = 1200,XXL = 1600,
}const screenMap = new Map<sizeEnum, screenEnum>()screenMap.set(sizeEnum.XS, screenEnum.XS)
screenMap.set(sizeEnum.SM, screenEnum.SM)
screenMap.set(sizeEnum.MD, screenEnum.MD)
screenMap.set(sizeEnum.LG, screenEnum.LG)
screenMap.set(sizeEnum.XL, screenEnum.XL)
screenMap.set(sizeEnum.XXL, screenEnum.XXL)export { screenMap }