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The JavaScript Interview Handbook: 100+ Interview Questions

Solution Review: Let's Curry!

This lesson will explain the solution to the problem in the previous lesson.

We'll cover the following...

Solution #

Javascript (babel-node)
function currying(func) {
    function curriedfunc(...args) {
        if(args.length >= func.length) {
            return func(...args);
        } else {
            return function(...next) {
                return curriedfunc(...args,...next);
            }
        }
    }
    return curriedfunc;
}
function multiply(a, b, c) {
    return a*b*c;
}
let curried = currying(multiply);
console.log(curried(2)(3)(4))
console.log(curried(2,3)(4))
console.log(curried(2,3,4))
console.log(curried(5)(6,7))

Explanation #

A simple approach for converting the multiply function to a curried function is:

Javascript (babel-node)
function multiply(a){
    return function(b){
      return function(c){
        return a*b*c
      }
  }
  
}
console.log(multiply(2)(3)(4))

However, the question requires you to write a function, currying, that takes any function and converts it into a currying function. So how do we do that?

  • First, we are passing the function, func, to our function, currying (line 1).

    function currying(func)

  • The next step is to think about the output. Re-stating the problem, we want to return a currying function. Hence, we define the function ...