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"
}
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
Typescript游乐场示例
enum TransactionStatus {
SUBMITTED = 'submitted',
APPROVED = 'approved',
PAID = 'paid',
CANCELLED = 'cancelled',
DECLINED = 'declined',
PROCESSING = 'processing',
}
let set1 = Object.entries(TransactionStatus).filter(([,value]) => value === TransactionStatus.SUBMITTED || value === TransactionStatus.CANCELLED).map(([key,]) => {
return key
})
let set2 = Object.entries(TransactionStatus).filter(([,value]) => value === TransactionStatus.PAID || value === TransactionStatus.APPROVED).map(([key,]) => {
return key
})
let allKeys = Object.keys(TransactionStatus)
console.log({set1,set2,allKeys})
其他回答
让ts-enum-util (github, npm)为您工作,并提供许多额外的类型安全实用程序。适用于字符串和数字enum,正确忽略数字enum的数字索引反向查找条目:
字符串枚举:
import {$enum} from "ts-enum-util";
enum Option {
OPTION1 = 'this is option 1',
OPTION2 = 'this is option 2'
}
// type: ("OPTION1" | "OPTION2")[]
// value: ["OPTION1", "OPTION2"]
const keys= $enum(Option).getKeys();
// type: Option[]
// value: ["this is option 1", "this is option 2"]
const values = $enum(Option).getValues();
数字枚举:
enum Option {
OPTION1,
OPTION2
}
// type: ("OPTION1" | "OPTION2")[]
// value: ["OPTION1", "OPTION2"]
const keys= $enum(Option).getKeys();
// type: Option[]
// value: [0, 1]
const values = $enum(Option).getValues();
如果你有enum
enum Diet {
KETO = "Ketogenic",
ATKINS = "Atkins",
PALEO = "Paleo",
DGAF = "Whatever"
}
然后你可以得到如下的键和值:
Object.keys(Diet).forEach((d: Diet) => {
console.log(d); // KETO
console.log(Diet[d]) // Ketogenic
});
在TypeScript中,一个enum在javascript中被编译成一个map(从键中获取值):
enum MyEnum {
entry0,
entry1,
}
console.log(MyEnum['entry0']); // 0
console.log(MyEnum['entry1']); // 1
它还创建了一个反向映射(从值中获取键):
console.log(MyEnum[0]); // 'entry0'
console.log(MyEnum[0]); // 'entry1'
所以你可以通过以下方式访问一个条目的名称:
console.log(MyEnum[MyEnum.entry0]); // 'entry0'
console.log(MyEnum[MyEnum.entry1]); // 'entry1'
但是,string enum在设计上没有反向映射(参见注释和pull request),因为这可能导致映射对象中的键和值之间的冲突。
enum MyEnum {
entry0 = 'value0',
entry1 = 'value1',
}
console.log(MyEnum['value0']); // undefined
console.log(MyEnum['value1']); // undefined
如果你想强制你的字符串enum编译一个反向映射(你必须确保所有的键和值都是不同的),你可以使用这个技巧:
enum MyEnum {
entry0 = <any>'value0',
entry1 = <any>'value1',
}
console.log(MyEnum['value0']); // 'entry0'
console.log(MyEnum['value1']); // 'entry1'
console.log(MyEnum[MyEnum.entry0]); // 'entry0'
console.log(MyEnum[MyEnum.entry1]); // 'entry1'
从TypeScript 2.4开始,枚举可以包含字符串初始化器https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-4.html
这允许你这样写:
enum Order {
ONE = "First",
TWO = "Second"
}
console.log(`One is ${Order.ONE.toString()}`);
得到这样的输出:
一个是First
基于上面的一些回答,我提出了这个类型安全的函数签名:
export function getStringValuesFromEnum<T>(myEnum: T): (keyof T)[] {
return Object.keys(myEnum).filter(k => typeof (myEnum as any)[k] === 'number') as any;
}
用法:
enum myEnum { entry1, entry2 };
const stringVals = getStringValuesFromEnum(myEnum);
stringVals的类型是'entry1' | 'entry2'
看看它的实际应用