Funsyn NPM | npm.io

funsyn

Lightweight functional syntax wrapper around JS built-in types' prototype methods; facilitates more consistent function composition.

So code you'd normally write like this, using functional ideas and object-oriented syntax:

[1, 2, 3, 4].map(n => n + 1).filter(n => n > 2);

Can be written like this:

var { map, filter } = require('funsyn').Array;

filter(map([1, 2, 3, 4], n => n + 1), n => n > 2);

With no significant dependencies (the code is < 500 bytes).

How to use

npm install funsyn

For any method you'd normally call on an instance -- say, 'derp'.split -- require the funsyn version of the function and invoke it by passing the instance as the first argument, followed by any subsequent arguments:

var split = require('funsyn').String.split;

split('derp');     // => ['derp']
split('derp', ''); // => ['d', 'e', 'r', 'p']

Everything is located at Type.method within funsyn (e.g., String.split).

Note: presently only works for Array, Date, Object, RegExp, and String prototype methods. Maybe others should be included; these seemed like the most obviously useful ones.

How it works

This package does very little: it iterates over the aforementioned prototypes and exports syntactically modified versions of their methods, which delegate calls to the original methods using fn.apply() and the instance.

Why

To facilitate more consistent function composition. For one thing, you can maintain consistency between the way built-in and not-built-in functions are invoked, without having to monkey-patch the shit out of the built-in types. Say you have a function that flattens a two-dimensional array:

function flatten(arr) {
  return [].concat.apply([], arr);
}

If you want to "work within" the existing system, you might find yourself wanting to do something like:

someArray.map(doSomeStuff).flatten();

Which is cool, but to implement this you have to do something like this:

Array.prototype.flatten = function() {
  return flatten(this);
};

Which is emphatically not cool (because it modifies Array.prototype). You could also do this:

flatten(someArray.map(doSomeStuff));

But it somewhat annoyingly mixes the two styles.

So this allows you to do:

flatten(map(someArray, doSomeStuff));

Without any significant library dependencies.

Worth noting: you can do stuff like this in Firefox already, e.g., String.split('derp', ''). I haven't seen it anywhere else though, hence this package.