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
试试这个
var color: color =(任何颜色)["绿色];
这对于3.5.3版本来说很好
其他回答
我需要知道如何循环枚举值(正在测试许多排列的几个enum),我发现这工作得很好:
export enum Environment {
Prod = "http://asdf.com",
Stage = "http://asdf1234.com",
Test = "http://asdfasdf.example.com"
}
Object.keys(Environment).forEach((environmentKeyValue) => {
const env = Environment[environmentKeyValue as keyof typeof Environment]
// env is now equivalent to Environment.Prod, Environment.Stage, or Environment.Test
}
来源:https://blog.mikeski.net/development/javascript/typescript-enums-to-from-string/
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');
如果您正在使用名称空间来扩展枚举的功能,那么您还可以这样做
enum Color {
Red, Green
}
export namespace Color {
export function getInstance(color: string) : Color {
if(color == 'Red') {
return Color.Red;
} else if (color == 'Green') {
return Color.Green;
}
}
}
像这样使用它
Color.getInstance('Red');
试试这个
var color: color =(任何颜色)["绿色];
这对于3.5.3版本来说很好
简单的方法
enum Color { Red, Green }
const c1 = Color["Red"]
const redStr = "Red" // important: use `const`, not mutable `let`
const c2 = Color[redStr]
这既适用于数值枚举,也适用于字符串枚举。不需要使用类型断言。
未知enum字符串
Simple, unsafe variantconst redStrWide: string = "Red" // wide, unspecific typed string
const c3 = Color[redStrWide as keyof typeof Color]
Safe variant with checks
const isEnumName = <T>(str: string, _enum: T): str is Extract<keyof T, string> =>
str in _enum
const enumFromName = <T>(name: string, _enum: T) => {
if (!isEnumName(name, _enum)) throw Error() // here fail fast as an example
return _enum[name]
}
const c4 = enumFromName(redStrWide, Color)
转换字符串enum值
字符串枚举没有反向映射(与数字枚举相反)。我们可以创建一个查找助手来将枚举值字符串转换为枚举类型:
enum ColorStr { Red = "red", Green = "green" }
const c5_by_name = ColorStr["Red"] // ✅ this works
const c5_by_value_error = ColorStr["red"] // ❌ , but this not
const enumFromValue = <T extends Record<string, string>>(val: string, _enum: T) => {
const enumName = (Object.keys(_enum) as Array<keyof T>).find(k => _enum[k] === val)
if (!enumName) throw Error() // here fail fast as an example
return _enum[enumName]
}
const c5 = enumFromValue("red", ColorStr)
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