What is currying and how does it work?

Currying is a technique in functional programming where a function that takes multiple arguments is transformed into a series of functions that each take a single argument. This allows for partial application of functions. For example, a function f(a, b, c) can be curried into f(a)(b)(c). Here's a simple example in JavaScript:

function add(a) {
  return function (b) {
    return function (c) {
      return a + b + c;
    };
  };
}

const addOne = add(1);
console.log(addOne); // function object

const addOneAndTwo = addOne(2);
console.log(addOneAndTwo); // function object

const result = addOneAndTwo(3);
console.log(result); // Output: 6