partial-application.js

let addOne
function add(x, y) { return x + y }

addOne = add.bind(null, 1)

addOne = x => add(1, x)

// new syntax
addOne = add(1, ?)

// all of the previous examples are equivalent
addOne(4) //=> 5

function concat(x, y, z) { return x + y + z }

const pad = concat('****', ?, '****')
pad('sup') //=> '****sup****'

const f = (x, ...y) => [x, ...y]
const g = f(?, 1, ...)
g(2, 3, 4); //=> [2, 1, 3, 4]