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    curry-arity

    1.0.0 • Public • Published

    curry-arity

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    Simple, tiny curry() and curryN() functions.

    Both can take functions of any arity, there are no limits.

    Resulting functions will always have the correct arity (length property).

    This library does not use eval(), new Function() or any dynamic code evaluation.

    Examples

    const f = (a, b, c) => a + b + c;
     
    const add = curry(f);
     
    add.length; // 3
    add(10).length; // 2
    add(10)(20).length; // 1
     
    add(10)(20)(30); // 60
    add(10, 20)(30); // 60
    add(10)(20, 30); // 60
    add(10, 20, 30); // 60
     
    /* reusable */
    const addTen = add(10); 
    addTen(20)(30); // 60
    addTen(40)(50); // 100

    Only the parameters before the first one with a default value are counted:

    const add = curry((a, b, c = 30) => a + b + c);
     
    add.length; // 2
    add(10)(20); // 60
    // add(10)(20)(70) would throw TypeError
     
    /* you can pass additional arguments in the final call */
    add(10)(20, 70); // 100

    You can also specify arity using curryN() instead of curry():

    const add = curryN(3, (a, b, c = 30) => a + b + c);
     
    add.length; // 3
    add(10)(20)(70); // 100
     
    /* undefined always triggers the default value */
    add(10)(20)(undefined); // 60

    Another example with curryN():

    const add = (...args) => args.reduce((a, b) => a + b);
     
    curryN(2, add).length;  // 2
    curryN(2, add)(10)(20); // 30
     
    curryN(3, add).length;  // 3
    curryN(3, add)(10)(20)(70); // 100

    Curried functions also correctly handle implicit this:

    const obj = {
      a: 10,
      addMe: curry(function (b, c) { return this.a + b + c; })
    }  
     
    /* 'this' from the first call (obj.addMe(20)) is always used */
    obj.addMe(20)(30); // 60 

    How it works

    Using Object.defineProperty() on created function objects. The original function object is not changed in any way.

    By the ES6 specification, function.length is configurable. It wasn't configurable in ES5.

    Supported Environments

    This library will not work in old ES5 browsers, namely IE11. By design, functions will throw if the length cannot be set, as the correct arity is a part of the API.

    The code is not transpiled to ES5, as the ES6 version is more efficient and the library wouldn't work in all ES5 browsers anyway. So, supported environments are:

    • Node >= 6
    • Browsers that support basic ES6 syntax

    Installation and Usage

    Node

    $ npm install curry-arity
    const { curry, curryN } = require('curry-arity');
     
    const f = (a, b, c = 30) => a + b + c;
     
    const fc = curry(f);
    console.log(fc(10)(20)); // 60
     
    const fc3 = curryN(3, f);
    console.log(fc3(10)(20)(70)); // 100

    Browser Script

    Unminified (~600B):

    <script src="https://unpkg.com/curry-arity@1.0.0/dist/curryarity.js"></script>

    or

    <script src="https://cdn.jsdelivr.net/npm/curry-arity@1.0.0/dist/curryarity.js"></script>

    Minified (~250B):

    <script src="https://unpkg.com/curry-arity@1.0.0/dist/curryarity.min.js"></script>

    or

    <script src="https://cdn.jsdelivr.net/npm/curry-arity@1.0.0/dist/curryarity.min.js"></script>

    The script creates a global variable CurryArity:

    const f = (a, b, c = 30) => a + b + c;
     
    const fc = CurryArity.curry(f);
    console.log(fc(10)(20)); // 60
     
    const fc3 = CurryArity.curryN(3, f);
    console.log(fc3(10)(20)(70)); // 100

    You can also install the package and take the scripts from the dist folder.

    ES Module

    $ npm install curry-arity

    ES module: ./node_modules/curry-arity/src/index.js

    If you are using Webpack, Rollup or any tool that reads from pkg.module, then simply:

    import { curry, curryN } from 'curry-arity';
     
    const f = (a, b, c = 30) => a + b + c;
     
    const fc = curry(f);
    const fc3 = curryN(3, f);

    and it will use the ES module directly, instead of the CommonJS version.

    API

    curry(f)

    Returns curried f, with the original arity.

    f

    Function of any arity.

    curryN(n, f)

    Returns curried f, with the specified arity.

    n

    Arity of the resulting function. Should be a non-negative integer.

    It can be less, equal or greater than the original arity.

    f

    Function of any arity.

    By design, the functions do not validate provided arguments.

    About

    Author

    Milos Djermanovic

    License

    MIT License

    Install

    npm i curry-arity

    DownloadsWeekly Downloads

    2

    Version

    1.0.0

    License

    MIT

    Unpacked Size

    10.2 kB

    Total Files

    7

    Last publish

    Collaborators

    • mdjermanovic