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A collection of ways for transforming functions

09 Jul 09:40
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A collection of ways for transforming functions.

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

A function is a set of statements that performs a task or calculates a value. It can accept some parameters, and may define some local variables necessary for performing the desired operation. These parameters and local variables are contained in the scope of the function, and cannot be accessed from the outside. However, a function can access variables external to itself (as long as they are not overridden), such as global variables or variables in the scope this function is encapsulated in. A nested function can access free variables that are defined in outer scopes, even when it is being invoked away from where it is defined. It does this by capturing the free variables (by reference) into a closure (1). Closure, arrow functions, and more, are functional language features based on lambda calculus.

This package includes a number of methods to transform functions. This enables you to obtain a desired function by transforming the behavior of existing functions (without actually executing them). The result of a function can be manipulated with [negate]. In case a pure function is expensive, its results can cached with [memoize]. Parameters of a function can be manipulated with [reverse], [spread], [unspread], [wrap], [unwrap]. [reverse] flips the order of parameters, [spread] spreads the first array parameter of a function, [unspread] combines all parameters into the first parameter (array), [wrap] adds ignored parameters to the left/right of a function's parameters, and [unwrap] removes common prefix and suffix parameters to a function (by passing known constant values as prefix/suffix). 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 [limitUse], [debounce], [debounceEarly], [throttle], [throttleEarly]. [limitUse] controls the number of times a function can be called, and is useful when you want to enforce a function to be called only once, the first n times (before), or after n times. [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 [limitUse], 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, isAsync, [isGenerator], [signature], [name], [parameters], and [arity] obtain metadata (about) information on a function. To attach a this to a function, use [bind]. A few generic functions are also included: ARGUMENTS, NOOP, IDENTITY, COMPARE.

This package is available in both Node.js and Web formats. The web format is exposed as extra_function standalone variable and can be loaded from jsDelivr CDN.

Stability: Experimental.


const funcxion = require('extra-function');
// import * as funcxion from "extra-function";
// import * as funcxion from "https://unpkg.com/extra-function/index.mjs"; (deno)

funcxion.composeRight(x => x*x, x => x+2);
// → 102

funcxion.curry((x, y) => x+y);
// → 7

funcxion.unspread(Math.max);
// → 1.25

funcxion.parameters((x, y) => x+y);
// → [ 'x', 'y' ]


Index

Property Description
ARGUMENTS Return the arguments passed as a array.
NOOP Do nothing.
IDENTITY Return the same (first) value.
COMPARE Compare two values.
is Check if value is a function.
isAsync Check if value is an async function.
[isGenerator] Check if value is a generator function.
[signature] Get the signature of a function.
[name] Get the name of a function.
[parameters] Get the parameter names of a function.
[arity] Get the number of parameters of a function.
[bind] Generate a function with bound this-object, and optional prefix arguments.
[negate] Generate a result-negated version of a function.
[memoize] Generate result-cached version of a 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.
[wrap] Generate a parameter-wrapped version of a function.
[unwrap] Generate a parameter-unwrapped version of a function.
[compose] Compose functions together, in applicative order.
[composeRight] Compose functions together, such that result is piped forward.
[curry] Generate curried version of a function.
[curryRight] Generate right-curried version of a function.
[delay] Generate delayed version of a function.
[limitUse] Generate limited-use version of a function.
[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




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