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Currying in JavaScript

Miscellaneous: Currying

What is currying in JavaScript?​

View Answer:
Interview Response: Currying is an advanced procedure for working with functions. It is used not only in JavaScript but in other languages as well. Currying is a transformation of functions that translates a function from callable as f(a, b, c) into callable as f(a)(b)(c). Currying does not call a function; it just transforms it. Currying allows us to extract partials quickly.

Code Example:

function curry(f) {
  // curry(f) does the currying transform
  return function (a) {
    return function (b) {
      return f(a, b);
    };
  };
}

// usage
function sum(a, b) {
  return a + b;
}

let curriedSum = curry(sum);

alert(curriedSum(1)(2)); // 3

What is the main rule of currying functions in JavaScript?​

View Answer:
Interview Response: Currying necessitates that a function takes a fixed number of arguments. A function with rest parameters, such as f(...args), cannot be curried in this manner.

Code Example: This is an example of Advanced Currying.

function curry(func) {
  return function curried(...args) {
    if (args.length >= func.length) {
      return func.apply(this, args);
    } else {
      return function (...args2) {
        return curried.apply(this, args.concat(args2));
      };
    }
  };
}

function sum(a, b, c) {
  return a + b + c;
}

let curriedSum = curry(sum);

alert(curriedSum(1, 2, 3)); // 6, still callable normally
alert(curriedSum(1)(2, 3)); // 6, currying of 1st arg
alert(curriedSum(1)(2)(3)); // 6, full currying