我在TypeScript中定义了以下enum:
enum Color{
Red, Green
}
现在在我的函数中,我以字符串的形式接收颜色。我尝试了以下代码:
var green= "Green";
var color : Color = <Color>green; // Error: can't convert string to enum
如何将该值转换为enum?
我在TypeScript中定义了以下enum:
enum Color{
Red, Green
}
现在在我的函数中,我以字符串的形式接收颜色。我尝试了以下代码:
var green= "Green";
var color : Color = <Color>green; // Error: can't convert string to enum
如何将该值转换为enum?
当前回答
枚举
enum MyEnum {
First,
Second,
Three
}
示例使用
const parsed = Parser.parseEnum('FiRsT', MyEnum);
// parsed = MyEnum.First
const parsedInvalid= Parser.parseEnum('other', MyEnum);
// parsedInvalid = undefined
忽略区分大小写的解析
class Parser {
public static parseEnum<T>(value: string, enumType: T): T[keyof T] | undefined {
if (!value) {
return undefined;
}
for (const property in enumType) {
const enumMember = enumType[property];
if (typeof enumMember === 'string') {
if (enumMember.toUpperCase() === value.toUpperCase()) {
const key = enumMember as string as keyof typeof enumType;
return enumType[key];
}
}
}
return undefined;
}
}
其他回答
对于Typescript >= 4,此代码工作:
enum Color{
Red, Green
}
// Conversion :
var green= "Green";
var color : Color = green as unknown as Color;
我得到了它的工作使用以下代码。
var green= "Green";
var color : Color= <Color>Color[green];
这些答案对我来说都太复杂了……
您可以简单地在枚举上创建一个解析函数,期望其中一个键作为参数。添加新颜色时,不需要进行其他更改
enum Color { red, green}
// Get the keys 'red' | 'green' (but not 'parse')
type ColorKey = keyof Omit<typeof Color, 'parse'>;
namespace Color {
export function parse(colorName: ColorKey ) {
return Color[colorName];
}
}
// The key 'red' exists as an enum so no warning is given
Color.parse('red'); // == Colors.red
// Without the 'any' cast you would get a compile-time warning
// Because 'foo' is not one of the keys in the enum
Color.parse('foo' as any); // == undefined
// Creates warning:
// "Argument of type '"bar"' is not assignable to parameter of type '"red" | "green"'"
Color.parse('bar');
它在TypeScript 4.4.3 TS游乐场链接中为我工作。
const stringToEnumValue = <T extends Record<string, string>, K extends keyof T>(
enumObj: T,
value: string,
): T[keyof T] | undefined =>
enumObj[
Object.keys(enumObj).filter(
(k) => enumObj[k as K].toString() === value,
)[0] as keyof typeof enumObj
];
enum Color {
Red = 'red',
Green = 'green',
}
const result1 = stringToEnumValue(Color, 'yellow'); // undefined
const result2 = stringToEnumValue(Color, 'green'); // Color.Green
console.log(result1) // undefined = undefined
console.log(result2) // Color.Green = "green"
Typescript 3.9提案
enum Color{ RED, GREEN }
const color = 'RED' as Color;
容易peasy……柠檬捏的!