An async function is a function that delivers its result asynchronously (through Promise).

📦 Node.js,
🌐 Web,
📜 Files,
📰 JSDoc,
📘 Wiki.

This package is an *variant* of extra-function, and includes methods for
transforming *async functions*. The **result** of an async function can be
manipulated with negate. If a *pure* async function is expensive, its results
can **cached** with memoize. **Parameters** of a function can be manipulated
with reverse, spread, unspread. reverse flips the order of parameters,
spread spreads the first array parameter of a function, and unspread
combines all parameters into the first parameter (array). If you want some
**functional behavior**, compose, composeRight, curry, and curryRight
can be used. composeRight is also known as pipe-forward operator or
function chaining. If you are unfamiliar, Haskell is a great purely
functional language, and there is great haskell beginner guide to learn from.

To control invocation **time** of a function, use delay. A function can be
**rate controlled** with debounce, debounceEarly, throttle,
throttleEarly. debounce and debounceEarly prevent the invocation of a
function during **hot** periods (when there are too many calls), and can be used
for example to issue AJAX request after user input has stopped (for certain
delay time). throttle and throttleEarly can be used to limit the rate of
invocation of a function, and can be used for example to minimize system usage
when a user is constantly refreshing a webpage. Except restrict, all
*rate/time control* methods can be *flushed* (`flush()`

) to invoke the target
function immediately, or *cleared* (`clear()`

) to disable invocation of the
target function.

In addition, is, name, and length obtain metadata (about) information on
an async function. To attach a `this`

to a function, use bind. A few generic
async functions are also included: ARGUMENTS, NOOP, IDENTITY, COMPARE.

This package is available in *Node.js* and *Web* formats. To use it on the web,
simply use the `extra_async_function`

global variable after loading with a `<script>`

tag from the jsDelivr CDN.

Stability: Experimental.

```
const xasyncfn = require('extra-async-function');
// import * as xasyncfn from "extra-async-function";
// import * as xasyncfn from "https://unpkg.com/extra-async-function/index.mjs"; (deno)
// 1. Basic tests.
async function example1() {
var a = xasyncfn.composeRight(async x => x*x, async x => x+2);
await a(10);
// → 102
var a = xasyncfn.curry(async (x, y) => x+y);
await a(2)(3);
// → 7
var a = xasyncfn.unspread(async (...xs) => Math.max(...xs));
await a([2, 3, 1]);
// → 1.25
}
example1();
```

## Index

Property | Description |
---|---|

ARGUMENTS | Resolve all the arguments passed, as an array. |

NOOP | Do nothing. |

IDENTITY | Return the same (first) value. |

COMPARE | Compare two async values. |

name | Get the name of a function. |

length | Get the number of parameters of a function. |

bind | Bind this-object, and optional prefix arguments to a function. |

call | Invoke a function with specified this-object, and arguments provided individually. |

apply | Invoke a function with specified this-object, and arguments provided as an array. |

is | Check if value is an async function. |

isGenerator | Check if value is a generator function. |

contextify | Contextify a function by accepting the first parameter as this-object. |

decontextify | Decontextify a function by accepting this-object as the first argument. |

negate | Generate a result-negated version of an async function. |

memoize | Generate result-cached version of an async function. |

reverse | Generate a parameter-reversed version of a function. |

spread | Generate a (first) parameter-spreaded version of a function. |

unspread | Generate a (first) parameter-collapsed version of a function. |

attach | Attach prefix arguments to leftmost parameters of a function. |

attachRight | Attach suffix arguments to rightmost parameters of a function. |

compose | Compose async functions together, in applicative order. |

composeRight | Compose async functions together, such that result is piped forward. |

curry | Generate curried version of a function. |

curryRight | Generate right-curried version of a function. |

defer | Generate deferred version of a function, that executes after the current stack has cleared. |

delay | Generate delayed version of a function. |

restrict | Generate restricted-use version of a function. |

restrictOnce | Restrict a function to be used only once. |

restrictBefore | Restrict a function to be used only upto a certain number of calls. |

restrictAfter | Restrict a function to be used only after a certain number of calls. |

debounce | Generate debounced version of a function. |

debounceEarly | Generate leading-edge debounced version of a function. |

throttle | Generate throttled version of a function. |

throttleEarly | Generate leading-edge throttled version of a function. |

## References

- MDN Web docs
- Lodash documentation
- Underscore.js documentation
- Function composition
- Debouncing and Throttling Explained Through Examples by David Corbacho
- Learn You a Haskell for Great Good!: Higher order functions by Miran Lipovaca
- Haskell composition (.) vs F#'s pipe forward operator (|>)
- memoizee package by Mariusz Nowak
- memoizerific package by @thinkloop
- compose-function package by Christoph Hermann
- chain-function package by Jason Quense
- extra-function package by Subhajit Sahu