Advanced freeCodeCamp • intermediate-algorithm-scripting

Arguments Optional

Challenge Overview

Create a function that sums two arguments together. If only one argument is provided, then return a function that expects one argument and returns the sum.

For example, addTogether(2, 3) should return 5, and addTogether(2) should return a function.

Calling this returned function with a single argument will then return the sum:

var sumTwoAnd = addTogether(2);

sumTwoAnd(3) returns 5.

If either argument isn’t a valid number, return undefined.

💡 View Solution

function addTogether() {
  const [first, second] = arguments;
  if (typeof first !== 'number') return undefined;
  if (arguments.length === 1) return (second) => (typeof second === 'number' ? first + second : undefined);
  if (typeof second !== 'number') return undefined;
  return first + second;
}