The Problem

Declare a function ‘multiplier’, which takes a number as an argument and returns another function. The returned function takes another number as an argument, and when invoked, it will return the product of the two numbers passed in.

This is a very simple example of how closure is used. We basically use the persistent memory of the outer function multiplier to remember outNum, the first number to be multiplied.

One solution

//i: number passed into outermost func
//o: product of number from outermost and number from innermost

// delcare function multiplier, takes in outNum
function multiplier(outNum){
	// return function which takes in inNum
  function inner(inNum){
		// return product of outNum and inNum
    return outNum * inNum;
  }
  return inner;
}
const test = multiplier(3);
console.log(test(5)) // 15
const test2 = multiplier(10);
console.log(test2(4)) // 40

Another solution

Almost exactly the same, just formatted slightly differently.

function multiplier(number1) {
  return function(number2) {
    return number1 * number2;
  }
}

const multiplyByFive = multiplier(5);
console.log(multiplyByFive(10)); // expected output: 50
console.log(multiplyByFive(7)); // expected output: 35