120 lines
3.1 KiB
TypeScript
120 lines
3.1 KiB
TypeScript
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/**
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* A helper for looking up TypeScript `enum` keys/values.
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*
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* @remarks
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* TypeScript enums implement a lookup table for mapping between their keys and values:
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*
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* ```ts
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* enum Colors {
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* Red = 1
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* }
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*
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* // Prints "Red"
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* console.log(Colors[1]);
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*
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* // Prints "1"
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* console.log(Colors["Red]);
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* ```
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*
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* However the compiler's "noImplicitAny" validation has trouble with these mappings, because
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* there are so many possible types for the map elements:
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*
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* ```ts
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* function f(s: string): Colors | undefined {
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* // (TS 7015) Element implicitly has an 'any' type because
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* // index expression is not of type 'number'.
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* return Colors[s];
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* }
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* ```
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*
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* The `Enum` helper provides a more specific, strongly typed way to access members:
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*
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* ```ts
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* function f(s: string): Colors | undefined {
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* return Enum.tryGetValueByKey(Colors, s);
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* }
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* ```
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*
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* @public
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*/
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export declare class Enum {
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private constructor();
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/**
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* Returns an enum value, given its key. Returns `undefined` if no matching key is found.
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*
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* @example
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*
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* Example usage:
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* ```ts
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* enum Colors {
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* Red = 1
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* }
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*
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* // Prints "1"
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* console.log(Enum.tryGetValueByKey(Colors, "Red"));
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*
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* // Prints "undefined"
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* console.log(Enum.tryGetValueByKey(Colors, "Black"));
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* ```
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*/
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static tryGetValueByKey<TEnumValue>(enumObject: {
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[key: string]: TEnumValue | string;
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[key: number]: TEnumValue | string;
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}, key: string): TEnumValue | undefined;
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/**
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* This API is similar to {@link Enum.tryGetValueByKey}, except that it throws an exception
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* if the key is undefined.
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*/
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static getValueByKey<TEnumValue>(enumObject: {
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[key: string]: TEnumValue | string;
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[key: number]: TEnumValue | string;
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}, key: string): TEnumValue;
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/**
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* Returns an enum string key, given its numeric value. Returns `undefined` if no matching value
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* is found.
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*
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* @remarks
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* The TypeScript compiler only creates a reverse mapping for enum members whose value is numeric.
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* For example:
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*
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* ```ts
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* enum E {
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* A = 1,
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* B = 'c'
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* }
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*
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* // Prints "A"
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* console.log(E[1]);
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*
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* // Prints "undefined"
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* console.log(E["c"]);
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* ```
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*
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* @example
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*
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* Example usage:
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* ```ts
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* enum Colors {
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* Red = 1,
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* Blue = 'blue'
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* }
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*
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* // Prints "Red"
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* console.log(Enum.tryGetKeyByNumber(Colors, 1));
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*
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* // Prints "undefined"
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* console.log(Enum.tryGetKeyByNumber(Colors, -1));
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* ```
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*/
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static tryGetKeyByNumber<TEnumValue, TEnumObject extends {
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[key: string]: TEnumValue;
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}>(enumObject: TEnumObject, value: number): keyof typeof enumObject | undefined;
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/**
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* This API is similar to {@link Enum.tryGetKeyByNumber}, except that it throws an exception
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* if the key is undefined.
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*/
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static getKeyByNumber<TEnumValue, TEnumObject extends {
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[key: string]: TEnumValue;
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}>(enumObject: TEnumObject, value: number): keyof typeof enumObject;
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}
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//# sourceMappingURL=Enum.d.ts.map
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