Is it possible to define an infix function?

Question

Is it possible to define my own infix function/operator in CoffeeScript (or in pure JavaScript)? e.g. I want to call

a foo b

or

Answer 1

ES6 enables a very Haskell/Lambda calculus way of doing things.

Given a multiplication function:

const multiply = a => b => (a * b)

You can define a doubling function using partial application (you leave out one parameter):

const double = multiply (2)

And you can compose the double function with itself, creating a quadruple function:

const compose = (f, g) => x => f(g(x))
const quadruple = compose (double, double)

But indeed, what if you would prefer an infix notation? As Steve Ladavich noted, you do need to extend a prototype.

But I think it can be done a bit more elegant using array notation instead of dot notation.

Lets use the official symbol for function composition "∘":

Function.prototype['∘'] = function(f){
  return x => this(f(x))
}

const multiply = a => b => (a * b)
const double = multiply (2)
const doublethreetimes = (double) ['∘'] (double) ['∘'] (double)

console.log(doublethreetimes(3));