bfe.dev #1

bfe-1-example.js

const  join = (a, b, c) => {
   return `${a}_${b}_${c}`
}

const curriedJoin = curry(join)

curriedJoin(1, 2, 3) // '1_2_3'

curriedJoin(1)(2, 3) // '1_2_3'

curriedJoin(1, 2)(3) // '1_2_3'

bfe1-solution.js

function curry(func) {
  return function curried(...args) {
    // 1. if enough args, call func 
    // 2. if not enough, bind the args and wait for new one
    if (args.length >= func.length) {
      return func.apply(this, args)
    } else {
      return curried.bind(this, ...args)
    }
  }
}