@mobily/ts-belt

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🔧 Fast, modern, and practical utility library for FP in TypeScript.

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TypeScript

import { Result } from '../Result'; import { ExtractValue } from '../types'; export declare type Option<A> = A | null | undefined; export declare const Some: <A>(value: NonNullable<A>) => Option<A>; export declare const None: Option<never>; /** Returns `Some(value)` if the provided value is non-nullable, otherwise, returns `None`. */ export declare function fromNullable<A>(value: A): Option<ExtractValue<A>>; /** Returns `Some(value)` if the provided value is not falsy, otherwise, returns `None`. */ export declare function fromFalsy<A>(value: A): Option<ExtractValue<A>>; /** Returns `Some(value)` if the given predicate function returns `true`, otherwise, returns `None`. */ export declare function fromPredicate<A>(value: A, predicateFn: (value: NonNullable<A>) => boolean): Option<ExtractValue<A>>; export declare function fromPredicate<A>(predicateFn: (value: NonNullable<A>) => boolean): (value: A) => Option<ExtractValue<A>>; /** Returns `Some(value)` (`value` is the result of `fn`) if `fn` didn't throw an error, otherwise, returns `None`. */ export declare function fromExecution<A>(fn: () => A): Option<ExtractValue<A>>; /** Returns `Some(value)` if `promise` is resolved successfully, otherwise, returns `None`. */ export declare function fromPromise<A>(promise: Promise<A>): Promise<Option<ExtractValue<A>>>; /** Returns the result of `mapFn` if `option` is `Some(value)`, otherwise, returns `None` and `mapFn` is not called. */ export declare function map<A, B>(option: Option<A>, mapFn: (value: A) => NonNullable): Option; export declare function map<A, B>(mapFn: (value: A) => NonNullable): (option: Option<A>) => Option; /** Returns the result of `mapFn` (it must have a return type of `Option`) if `option` is `Some(value)`, otherwise, returns `None`. */ export declare function flatMap<A, B>(option: Option<A>, mapFn: (value: A) => Option): Option; export declare function flatMap<A, B>(mapFn: (value: A) => Option): (option: Option<A>) => Option; /** Returns the result of `mapFn` if `option` is `Some(value)`, otherwise, returns a default value. */ export declare function mapWithDefault<A, B>(option: Option<A>, defaultValue: NonNullable, mapFn: (value: A) => B): B; export declare function mapWithDefault<A, B>(defaultValue: NonNullable, mapFn: (value: A) => B): (option: Option<A>) => B; /** Returns `Some(value)` if the result of `mapFn` is non-nullable, otherwise, returns `None`. */ export declare function mapNullable<A, B>(option: Option<A>, mapFn: (value: A) => B | null | undefined): Option<ExtractValue>; export declare function mapNullable<A, B>(mapFn: (value: A) => B | null | undefined): (option: Option<A>) => Option<ExtractValue>; /** Returns `Some(value)` if `option` is `Some(value)` and the result of `predicateFn` is truthy, otherwise, returns `None`. */ export declare function filter<A>(option: Option<A>, predicateFn: (value: A) => boolean): Option<A>; export declare function filter<A>(predicateFn: (value: A) => boolean): (option: Option<A>) => Option<A>; /** Returns `value` if `option` is `Some(value)`, otherwise, returns a default value. */ export declare function getWithDefault<A>(option: Option<A>, defaultValue: NonNullable<A>): A; export declare function getWithDefault<A>(defaultValue: NonNullable<A>): (option: Option<A>) => A; /** Returns `value` if `option` is `Some(value)`, otherwise, throws an exception. */ export declare function getExn<A>(option: Option<A>): A | never; /** Returns `value` if `option` is `Some(value)`, otherwise, returns `null`. */ export declare function toNullable<A>(option: Option<A>): A | null; /** Returns `value` if `option` is `Some(value)`, otherwise, returns `undefined`. */ export declare function toUndefined<A>(option: Option<A>): A | undefined; /** Returns `Ok(value)` if `option` is `Some(value)`, otherwise, returns `Error(errorValue)`, both `Ok` and `Error` come from the `Result` type. */ export declare function toResult<A, B>(option: Option<A>, errorValue: NonNullable): Result<A, B>; export declare function toResult<A, B>(errorValue: NonNullable): (option: Option<A>) => Result<A, B>; /** Returns the result of `someFn` if `option` is `Some(value)`, otherwise, returns the result of `noneFn`. */ export declare function match<A, B>(option: Option<A>, someFn: (value: A) => B, noneFn: () => B): B; export declare function match<A, B>(someFn: (value: A) => B, noneFn: () => B): (option: Option<A>) => B; /** Returns `true` if the provided `option` is `None`, otherwise, returns `false`. */ export declare function isNone<A>(option: Option<A>): option is Option<never>; /** Returns `true` if the provided `option` is `Some(value)`, otherwise, returns `false`. */ export declare function isSome<A>(option: Option<A>): option is Option<A>; /** Applies a side-effect function to the value in `Some`, and returns the original `option`. */ export declare function tap<A>(option: Option<A>, someFn: (value: A) => void): Option<A>; export declare function tap<A>(someFn: (value: A) => void): (option: Option<A>) => Option<A>; /** Checks if `option` is the `Some` variant and contains the given value. */ export declare function contains<A>(option: Option<A>, value: any): boolean; export declare function contains<A>(value: any): (option: Option<A>) => boolean; /** Combines two Options into a single Option containing a tuple of their values, if both Options are `Some` variants, otherwise, returns `None`. */ export declare function zip<A, B>(sndOption: Option): (fstOption: Option<A>) => Option<readonly [A, B]>; export declare function zip<A, B>(fstOption: Option<A>, sndOption: Option): Option<readonly [A, B]>; /** Combines two Options into a single Option. The new value is produced by applying the given function to both values, if both Options are `Some` variants, otherwise, returns `None`. */ export declare function zipWith<A, B, C>(fstOption: Option<A>, sndOption: Option, mapFn: (arg0: A, arg1: B) => Option<C>): Option<C>; export declare function zipWith<A, B, C>(sndOption: Option, mapFn: (arg0: A, arg1: B) => Option<C>): (fstOption: Option<A>) => Option<C>;