LeetCode FizzBuzz Solution explained

fizzBuzz.js

var fizzBuzz = function(n) {
    // Start by creating an empty list to store our result
    var result = []
    // Then we iterate from 1 to the number input
    for (let i = 1; i <= n; i++) {
        /**
         * This output variable is where we are
         * storing either Fizz, Buzz or the number
         * we are currently iterating.
         * 
         * Notice how I am not storing anything to
         * the result variable until the end
         */
        let output = ''
        /**
         * The modular operator (%) returns the remainder
         * of a division.
         * 
         * For example, if we need to check if a number is even,
         * we can do that this way: 
         * 
         * const number = 4
         * if (number % 2 == 0) { 'number is even, because 4 / 2 = 2 and the remainder is 0' }
         */

        // So now, if the number i is multiple of 3, we add Fizz to the output.
        if(i % 3 == 0) output += 'Fizz'
        // If the number i is multiple of 5, we add Buzz to the output
        if(i % 5 == 0) output += 'Buzz'
        /**
         * If the number is multiple of 3 AND 5, both conditions are true and
         * both strings will concatenate, getting 'FizzBuzz' in the output variable.
         */

        /**
         * Next, we check the output variable to see if it is empty.
         * If it is, that means that the number i isn't multiple of 3 or 5.
         * 
         * We can check it out with an if this way:
         * 
         * if (output == '') {
         *  result.push(`${i}`)
         * } else {
         *  result.push( output )
         * }
         * 
         * Checking if the output variable is empty is way faster than 
         * adding a third condition to the algorithm, wich could be:
         * 
         * if ( i % 3 !== 0 and i % 5 !== 0 ) { output = i }
         * 
         * This looks 'fine' in this example but if in the future somebody asks
         * to check if the number is multiple of 3, 5, 7, 9, 17, etc,
         * you should add a new condition in this line, making it not so clean code.
         */

        /**
         * To make the code even shorter I'm using the OR operator (||)
         * to check if the output variable is empty.
         * 
         * An empty string ('') if a falsy value in javascript, so
         * that's why it pushes the number itself instead of the output variable, if it's empty.
         */
        result.push(output || `${i}`)
        // I'm using a template string `${i}` wich is a shorter way in this case to cast the number to a String
    }
    // Finally, we return the result list.
    return result
}