我想迭代一个TypeScript枚举对象,并获得每个枚举符号名称,例如: enum myEnum {entry1, entry2}

for (var entry in myEnum) { 
    // use entry's name here, e.g., "entry1"
}

当前回答

我的Enum是这样的:

export enum UserSorting {
    SortByFullName = "Sort by FullName", 
    SortByLastname = "Sort by Lastame", 
    SortByEmail = "Sort by Email", 
    SortByRoleName = "Sort by Role", 
    SortByCreatedAt = "Sort by Creation date", 
    SortByCreatedBy = "Sort by Author", 
    SortByUpdatedAt = "Sort by Edit date", 
    SortByUpdatedBy = "Sort by Editor", 
}

这样做会返回undefined:

UserSorting[UserSorting.SortByUpdatedAt]

为了解决这个问题,我选择了另一种使用管道的方法:

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
    name: 'enumKey'
})
export class EnumKeyPipe implements PipeTransform {

  transform(value, args: string[] = null): any {
    let enumValue = args[0];
    var keys = Object.keys(value);
    var values = Object.values(value);
    for (var i = 0; i < keys.length; i++) {
      if (values[i] == enumValue) {
        return keys[i];
      }
    }
    return null;
    }
}

要使用它:

return this.enumKeyPipe.transform(UserSorting, [UserSorting.SortByUpdatedAt]);

其他回答

如果它是你的枚举,你定义如下所示,名称和值是相同的,它会直接给你条目的名称。

enum myEnum { 
    entry1="entry1", 
    entry2="entry2"
 }

for (var entry in myEnum) { 
    // use entry's name here, e.g., "entry1"
}

如果你想在html中获取名字

对于这个枚举

enum CanadianProvinces {
    AB,
    BC,
    MB,
    NB,
    NL,
    NT,
    NS,
    NU,
    ON,
    PE,
    QC,
    SK,
    YT
}

将组件中的变量赋值为

canadianProvinces = CanadianProvinces 

然后,在你的html

{{canadianProvinces[0]}}

对我来说,一个更简单、实用和直接的方法来理解正在发生的事情,就是下面的列举:

enum colors { red, green, blue };

本质上将转换为:

var colors = { red: 0, green: 1, blue: 2,
               [0]: "red", [1]: "green", [2]: "blue" }

正因为如此,以下情况将是正确的:

colors.red === 0
colors[colors.red] === "red"
colors["red"] === 0

这创建了一个简单的方法来获取枚举的名称,如下所示:

var color: colors = colors.red;
console.log("The color selected is " + colors[color]);

它还创建了一种将字符串转换为枚举值的好方法。

var colorName: string = "green";
var color: colors = colors.red;
if (colorName in colors) color = colors[colorName];

以上两种情况更为常见,因为通常您对特定值的名称和以通用方式序列化值更感兴趣。

我卑微的2美分基于阅读一个了不起的评论从github TS讨论

const EnvironmentVariants = ['development', 'production', 'test'] as const 
type EPredefinedEnvironment = typeof EnvironmentVariants[number]

然后在编译时:

// TS2322: Type '"qaEnv"' is not assignable to type '"development" | "production" | "test"'.
const qaEnv: EPredefinedEnvironment = 'qa' 

在运行时:

function isPredefinedEnvironemt(env: string) {
  for (const predefined of EnvironmentVariants) {
    if (predefined === env) {
      return true
    }
  }
  return false
}

assert(isPredefinedEnvironemet('test'), true)
assert(isPredefinedEnvironemet('qa'), false)

注意,for(const index in environmentvariables){…}将遍历"0","1","2"集合

这个解决方案也可以。

enum ScreenType {
    Edit = 1,
    New = 2,
    View = 4
}

var type: ScreenType = ScreenType.Edit;

console.log(ScreenType[type]); //Edit