ulyssesdotcodes/effing

Function functions.

effing.js

Some handy function functions for JavaScript, minus the docs and examples and such.

• easy partial application: f(func, arg)
• easy function binding: f(obj, method)
• easy both at the same time: f(obj, method, arg)
• function equivalents for operators: [1, 2, 3].reduce(f.add)
• partial application for operators: [-3, 4, 2].filter(f.gt(0))

Functionoids

The following things are coerced into functions by effing.js:

• null becomes a no-op function
• undefined becomes a no-op function
• [fn, args...] becomes a partially applied function
• [context, method, args...] becomes a partially applied function with a bound context
• [context, 'methodName', args...] becomes a partially applied function with a bound context by looking up the specified key on the context

Anywhere effing.js expects a function argument, it will be happy with a functionoid instead.

Note that the [context, ...] functionoids don't allow Functions to be used as contexts. effing.js can't read your mind.

Functionoid conversion

effing.js exports a function, usually called f, that will convert functionoids into normal functions.

When called with one argument, it follows the rules above. When called with no arguments, it returns a no-op function. When called with more than one argument, it behaves as if it were invoked with the arguments in a list.

So f(fn, arg) produces a partially applied function, for example, as if you had called f([fn, arg]).

Operators

Logical operators

operator	name
&&	and
`
!	not

Comparison operators

operator	name
<	lt
>	gt
<=	lte
>=	gte
===	eq
!==	neq

Numeric operators

operator	name	alias
+	add
-	subtract	sub
*	multiply	mult
/	divide	div
%	remainder	rem
-	negate	neg

effing.js also has some numeric operators that JavaScript doesn't have:

name	alias	description
modulo	mod	Like JavaScript's remainder operator, but will never produce a negative value.
intDivide	idiv	Floor division.

Partial application for binary operators

In Haskell you can say:

isMinor = (< 18)

In f'ing JavaScript, you have to say:

var isMinor = f.lt(18);

When you invoke any of the binary operator functions with a single argument, it will alaways fill in the right side of the operator. To fill in the left argument, you can use normal functionoid partial application: f(f.lt, 18).