Software Engineering Coding Challenge 3 (Javascript)

/**
 * Requirements:
 * Write a function that accepts a string and returns the number of words in the given string.
 * Also make your function resilient (i.e., handling different inputs).
 *
 * Write your solution without using any libraries and use ES6 or above as much as possible.
 */

function countWords(sentence) {}

let sentence = 'A quick brown fox jumps over the lazy dog';
countWords(sentence); // Output: 9