cond

util

Creates a function that iterates over pairs and invokes the corresponding function of the first predicate to return truthy.

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Installation

Import

import { cond } from '@tulx/utils';

Source Code

Implementation

/**
 * Creates a function that iterates over pairs and invokes the corresponding function of the first predicate to return truthy.
 *
 * @param pairs - The predicate-function pairs.
 * @returns Returns the new composite function.
 *
 * @example
 * ```ts
 * const func = cond([
 *   [matches({ 'user': 'barney' }), () => 'A'],
 *   [matches({ 'age': 36 }), () => 'B'],
 *   [stubTrue, () => 'C']
 * ]);
 * func({ 'user': 'barney', 'active': false }); // 'A'
 * func({ 'user': 'fred', 'age': 36 }); // 'B'
 * func({ 'user': 'pebbles', 'age': 1 }); // 'C'
 * ```
 */
export function cond<T, R>(
  pairs: readonly [(value: T) => boolean, (value: T) => R][]
): (value: T) => R | undefined {
  return function (value: T): R | undefined {
    for (const [predicate, func] of pairs) {
      if (predicate(value)) {
        return func(value);
      }
    }
    return undefined;
  };
}

Example

import { cond } from '@tulx/utils';

const func = cond([
[matches({ 'user': 'barney' }), () => 'A'],
[matches({ 'age': 36 }), () => 'B'],
[stubTrue, () => 'C']
]);
func({ 'user': 'barney', 'active': false }); // 'A'
func({ 'user': 'fred', 'age': 36 }); // 'B'
func({ 'user': 'pebbles', 'age': 1 }); // 'C'

Related Functions

attempt

Attempts to invoke func, returning either the result or the caught error object.

bindAll

Binds methods of an object to the object itself, overwriting the existing method.

conforms

Creates a function that invokes the predicate properties of source with the corresponding property values of a given object.

constant

Creates a function that returns value.

defaultTo

Checks value to determine whether a default value should be returned in its place.

flow

Creates a function that returns the result of invoking the given functions with the this binding of the created function.