feat(isDigit): add isDigit type#6
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WalkthroughThe pull request introduces a set of TypeScript utility types for checking whether a given type represents a digit string. These types are implemented across three files in the Changes
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Actionable comments posted: 1
🧹 Nitpick comments (4)
src/string/isDigit/algo.ts (2)
3-7: Consider adding JSDoc comments for the _IsDigit type.While the implementation is correct, adding documentation would help explain the purpose of this internal utility type and its expected behavior.
+/** + * Internal utility type that checks if a type parameter extends a numeric string pattern. + * @template T - The type to check + * @returns {boolean} - True if T extends `${number}`, false otherwise + * @internal + */ export type _IsDigit<T> = [T] extends [ `${number}`, ] ? true : false
9-14: Consider renaming IsDigit_Back and adding documentation.The "_Back" suffix is unclear. If this is an alternative implementation, consider a more descriptive name like "IsDigitStrict" since it adds string literal validation.
+/** + * Strict type guard that checks if a type parameter is both a string literal + * and matches a numeric string pattern. + * @template T - The type to check + * @returns {boolean} - True if T is a string literal and extends `${number}`, false otherwise + */ -export type IsDigit_Back<T> = +export type IsDigitStrict<T> = IsStringLiteral<T> extends true ? [T] extends [`${number}`] ? true : false : falsesrc/string/isDigit/index.test.ts (2)
12-44: Add tests for additional numeric string patterns.The test suite is thorough but could be expanded to cover more edge cases:
- Scientific notation (e.g., "1e5")
- Negative numbers (e.g., "-123")
- Leading/trailing whitespace
describe("_IsDigit type tests", () => { it("should return true for string literals that match numeric patterns", () => { type T1 = _IsDigit<"0"> type T2 = _IsDigit<"123"> type T3 = _IsDigit<"001"> type T4 = _IsDigit<"1.2"> + type T5 = _IsDigit<"-123"> + type T6 = _IsDigit<"1e5"> expectTypeOf<T1>().toEqualTypeOf<true>() expectTypeOf<T2>().toEqualTypeOf<true>() expectTypeOf<T3>().toEqualTypeOf<true>() expectTypeOf<T4>().toEqualTypeOf<true>() + expectTypeOf<T5>().toEqualTypeOf<true>() + expectTypeOf<T6>().toEqualTypeOf<true>() }) it("should return false for string literals that are not numeric", () => { type T1 = _IsDigit<""> type T2 = _IsDigit<"abc"> type T3 = _IsDigit<"1a2"> type T4 = _IsDigit<"one"> + type T5 = _IsDigit<" 123 "> expectTypeOf<T1>().toEqualTypeOf<false>() expectTypeOf<T2>().toEqualTypeOf<false>() expectTypeOf<T3>().toEqualTypeOf<false>() expectTypeOf<T4>().toEqualTypeOf<false>() + expectTypeOf<T5>().toEqualTypeOf<false>() })
76-87: Improve comments for union type tests.The current comments about IsStringLiteral are repeated and could be more precise about the expected behavior with unions.
- // If IsStringLiteral is strictly checking for a single literal type, - // then a union of two string literals is not "a single literal." + // Test that a union containing any non-digit string literal evaluates to false type T1 = IsDigit_Back<"123" | "abc" | "234"> expectTypeOf<T1>().toEqualTypeOf<false>() }) it("should return true when given a union of string literals (all digits)", () => { - // If IsStringLiteral is strictly checking for a single literal type, - // then a union of two string literals is not "a single literal." + // Test that a union of only digit string literals evaluates to true type T1 = IsDigit_Back<"123" | "345" | "1214"> expectTypeOf<T1>().toEqualTypeOf<true>() })
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📒 Files selected for processing (3)
src/string/isDigit/algo.ts(1 hunks)src/string/isDigit/index.test.ts(1 hunks)src/string/isDigit/index.ts(1 hunks)
| /** | ||
| * A type that returns true if a param is a stringified number, and false otherwise. | ||
| * | ||
| * @template Str - The string literal type to reverse. | ||
| * @returns {string} - Returns the reversed string. | ||
| */ |
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Fix incorrect JSDoc documentation.
The current documentation has incorrect template parameter description and return type. It appears to be copied from a string reversal utility.
/**
* A type that returns true if a param is a stringified number, and false otherwise.
*
- * @template Str - The string literal type to reverse.
- * @returns {string} - Returns the reversed string.
+ * @template T - The string type to check.
+ * @returns {boolean} - Returns true if T represents a valid numeric string, false otherwise.
+ * @example
+ * type T1 = IsDigit<"123"> // true
+ * type T2 = IsDigit<"abc"> // false
+ * type T3 = IsDigit<"1.2"> // true
+ * type T4 = IsDigit<""> // false
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| /** | |
| * A type that returns true if a param is a stringified number, and false otherwise. | |
| * | |
| * @template Str - The string literal type to reverse. | |
| * @returns {string} - Returns the reversed string. | |
| */ | |
| /** | |
| * A type that returns true if a param is a stringified number, and false otherwise. | |
| * | |
| * @template T - The string type to check. | |
| * @returns {boolean} - Returns true if T represents a valid numeric string, false otherwise. | |
| * @example | |
| * type T1 = IsDigit<"123"> // true | |
| * type T2 = IsDigit<"abc"> // false | |
| * type T3 = IsDigit<"1.2"> // true | |
| * type T4 = IsDigit<""> // false | |
| */ |
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Summary by CodeRabbit
New Features
IsDigitfor compile-time validation of numeric string typesTests