func-utils v0.0.1

func-utils

Utility functions for functional programming in Node.js

Functions

f.arg ( n )

Returns the nth argument on each call.

var second = f.arg(2);

second('a', 'b', 'c');
// "b"

f.first / f.identity ( void )

Aliases for f.arg(1), always returns the first argument on each call.

f.nth ( n, offset )

Returns true on each nth call to the function, and false on every other call.

var evenOnly = f.nth(2);

evenOnly();  // false
evenOnly();  // true
evenOnly();  // false
evenOnly();  // true

var oddOnly = f.nth(2, 1);

oddOnly(); // true
oddOnly(); // false
oddOnly(); // true

f.odd / f.even ( void )

Aliases for f.nth(2) and f.nth(2, 1).

var nums = [1, 2, 3, 4, 5, 6, 7];

nums.filter(f.odd());
// [1, 3, 5, 7]

nums.filter(f.even());
// [2, 4, 6]

f.iota ([ start, skip ])

Returns an increasing value with each call.

var iota = f.iota();

iota(); // 1
iota(); // 2
iota(); // 3

iota = f.iota(1, 2);

iota(); // 1
iota(); // 3
iota(); // 5

f.not ( func )

Returns a new function that calls through to the given function, but returns a negated return value.

var alwaysTrue = function() {
	return true;
};

var alwaysFalse = f.not(alwaysTrue);

alwaysTrue(); // true
alwaysFalse(); // false

f.pick ( prop )

Selects a specific named property from objects.

var people = [
	{name: 'bob', gender: 'male', age: 23},
	{name: 'sarah', gender: 'female', age: 19}
];

var names = people.map(f.pick('name'));
// [ "bob", "sarah" ]

f.filterMap ( filter, map )

Filter and map in one iteration using a reduce.

var people = [
	{name: 'bob', gender: 'male', age: 23},
	{name: 'sarah', gender: 'female', age: 19},
	{name: 'sally', gender: 'female', age: 25}
];

var girlsOnly = function(person) {
	return person.gender === 'female';
};

var getName = function(person) {
	return person.name;
};

var girlsNames = people.reduce(f.filterMap(girlsOnly, getName));
// [ "sarah", "sally" ]

f.where ( prop, value )

Return true for objects where the object's property prop matches the given value.

var people = [
	{name: 'bob', gender: 'male', age: 23},
	{name: 'sarah', gender: 'female', age: 19},
	{name: 'sally', gender: 'female', age: 25}
];

var girls = people.filter(f.where('gender', 'female'));