narrow-minded/dist/narrow.d.ts

Easy typeof validations with sophisticated TypeScript inference.

import { NarrowerArr, NarrowerObj, NarrowerSome, Primitive, UnNarrow } from './schema';
/**
 * This function validates any value with `typeof` checks. Arrays and objects are traversed
 * according to the Narrower structure. The boolean return value is also a TypeScript type
 * predicate.
 *
 * **Objects** -
 * All keys of `n` are checked against `u` and their narrow is validated if the key exists.
 * Keys that are missing from `u` are treated as having the value `undefined`. This means
 * you can use `{ key: some('undefined', ...)}` to allow for missing/optional keys.
 *
 * **Arrays** -
 * Including multiple types in a Narrower array allows for mixed types. Each item in `u` must
 * satisfy at least one of the types.
 *
 * **Null** -
 * `typeof null` is `'object'` but null cannot have any keys. Use `{}` to match an object
 * that is not null.
 *
 * @example
 * // An array of mixed strings and numbers:
 * narrow(['string', 'number'], [1, 'two']) //=> true
 * narrow(['string', 'number'], [{}]) //=> false
 *
 * // Null:
 * narrow('object', null) //=> true
 * narrow({}, null) //=> false
 *
 * // A deep object:
 * narrow({
 * 	n: 'number',
 * 	child: {
 * 		word: 'string'
 * 	},
 * 	things: [
 * 		['number'],
 * 		'boolean'
 * 	],
 * }, {
 * 	n: 3.14,
 * 	child: {
 * 		word: 'Yes'
 * 	},
 * 	things: [
 * 		false,
 * 		[1, 2, 3],
 * 		true
 * 	]
 * }) //=> true
 *
 * @param n The Narrower schema.
 * @param u The value of unknown type to validate.
 * @returns A type predicate that `u` satisfies `n`.
 */
export declare const narrow: <N extends Primitive | NarrowerArr | NarrowerObj | NarrowerSome>(n: N, u: unknown) => u is UnNarrow<N>;
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