Functools


> Utilities for working with functions in JavaScript, with TypeScript.

_(Inspired by functools of the same name)_

Installation

``
npm install functools --save
`

Usage

$3

Always returns the same value supplied to it.

`js
identity(42); //=> 42
`

$3

Returns a function that always returns the same value supplied to it.

`js
identity(42); //=> 42
`

$3

Optimize a function to speed up consecutive calls by caching the result of calls with identical input arguments. The cache can be overridden for features such as an LRU cache.

`js
let i = 0;
const fn = memoize(() => ++i);

fn("foo"); //=> 1
fn("foo"); //=> 1

fn("bar"); //=> 2
fn("bar"); //=> 2
`

$3

Memoize the result of fn after the first invocation.

`js
let i = 0;
const fn = memoize0(() => ++i);

fn(); // => 1
fn(); // => 1
fn(); // => 1
`

$3

Memoize the result of a function based on the most recent arguments.

`js
let i = 0;
const fn = memoize(() => ++i);

fn("foo"); //=> 1
fn("foo"); //=> 1

fn("bar"); //=> 2
fn("bar"); //=> 2

fn("foo"); //=> 3
fn("foo"); //=> 3
`

$3

Return a function that fetches key from its operand.

`js
prop("foo")({ foo: 123 }); //=> 123
`

$3

Return a function that calls the method name on its operand. If additional arguments are given, they will be given to the method as well.

`js
invoke("add", 5, 5)({ add: (a, b) => a + b }); //=> 10
`

$3

Wrap a function to rate-limit the function executions to once every ms milliseconds.

`js
let i = 0
const fn = throttle(() => ++i, 100)

fn() // i == 1
fn() // i == 1
fn() // i == 1

setTimeout(() => / i == 2 /, 200)
`

Tip: Use fn.clear and fn.flush for finer execution control.

- fn.clear Unconditionally clears the current timeout
- fn.flush When fn is pending, executes fn() and starts a new interval

$3

Given a fn, return a wrapper that accepts an array of fn arguments.

`js
Promise.all([1, 2, 3]).then(spread(add));
`

$3

Flip a binary fn argument order.

`js
flip(subtract)(5, 10); //=> 5
`

$3

Returns a partially applied fn with the supplied arguments.

`js
partial(subtract, 10)(5); //=> 5
`

$3

Left-to-right function composition.

`js
sequence(partial(add, 10), partial(multiply, 5))(5); //=> 75
`

$3

Right-to-left function composition.

`js
compose(partial(add, 10), partial(multiply, 5))(5); //=> 35
`

$3

Fix the number of receivable arguments in origFn to n.

`js
["1", "2", "3"].map(nary(1, fn)); //=> [1, 2, 3]
``

TypeScript

This module uses TypeScript and publishes type definitions on NPM.

License

Apache 2.0