fn.map

Function binding with argument mapping.

For too long in Javascript I have used this pattern.

function doSomething(callback) {
	// .. get some data
	callback(stuff, otherStuff)
}

function doSomethingElse(otherStuff) {
	// .. do something else
}

// I only need `otherValues` but I get `values` with it
// This prevents me from simply:
// soSomething(doSomethingElse.bind(null));

doSomething(function(values, otherValues) {
	doSomethingElse(otherValues)
});

Don't see anything wrong? I do, an extra callback! I should just be able to bind that function and forget about creating another function to just essentially move on argument to another position. It really impairs any functional style of Javascript, well at least I think so anyway. With map, you can do the following:

// Map the second argument to the first position (null is the context, similar to .bind)
doSomething(map(doSomethingElse, null, map.$2));

Installation

Install from npm:

$ npm install --save fn.map

map(fn {function}, context {object}, args..{ map.$* | anything }) -> Function

Take in a function, bind it to a context and return another function that maps incoming arguments to the inital function.

Examples

Want to log something in array but don't want those pesky indexes and the array arguments?

var a = [1, 2, 3, 4];

a.forEach(map(console.log, console, map.$1)); // Only log the numbers

Want to map over values returned from a previous function in the waterfall chain in async?

async.waterfall([
	getSomeValues.bind(null, "some argument"),
	map(async.eachSeries, async, map.$1, function iterator(value) {
		console.log("Values!");
	}, map.$2) // Don't forget to map the passed callback!
])

License: MIT