Simpler boolean returns in functions with JavaScript

Yesterday, I wrote about how to simplify complex if statements by breaking them into smaller pieces

We ended up with a function that looked like this…

/**
 * Is a creature magical?
 * @param  {String}  creature The type of creature
 * @param  {String}  tool     The magical tool they have, if any
 * @return {Boolean}          If true, they're magical
 */
function isMagical (creature, tool) {

	// Checks
	let isUnicorn = creature === 'unicorn';
	let isElf = creature === 'elf';
	let isMagicGnome = creature === 'gnome' && tool === 'alchemy';
	let isMagicHuman = creature === 'human' && tool === 'wand';

	// If the creature is magical return true
	// Otherwise return false
	if (isUnicorn || isElf || isMagicGnome || isMagicHuman) return true;
	return false;

}

But as one astute reader pointed out, all of the is* variables are boolean values: either true or false.

As a result, we can return the variables themselves, with or operators (||), and skip the if () return entirely.

/**
 * Is a creature magical?
 * @param  {String}  creature The type of creature
 * @param  {String}  tool     The magical tool they have, if any
 * @return {Boolean}          If true, they're magical
 */
function isMagical (creature, tool) {

	// Checks
	let isUnicorn = creature === 'unicorn';
	let isElf = creature === 'elf';
	let isMagicGnome = creature === 'gnome' && tool === 'alchemy';
	let isMagicHuman = creature === 'human' && tool === 'wand';

	// If the creature is magical return true
	// Otherwise return false
	return isUnicorn || isElf || isMagicGnome || isMagicHuman;

}

This is a great pattern to use in functions that do simple checks, as well.

Instead of doing this…

/**
 * Check if an expiration date is after the current date
 * @param  {Integer}  expires The expiration date as a timestamp
 * @return {Boolean}          If true, date is still valid
 */
function isValid (expires) {
	if (expires < Date.now()) {
		return true;
	} else {
		return false;
	}
}

You could do this…

/**
 * Check if an expiration date is after the current date
 * @param  {Integer}  expires The expiration date as a timestamp
 * @return {Boolean}          If true, date is still valid
 */
function isValid (expires) {
	return expires < Date.now();
}

Another reader pointed out that the isMagical() function could use the early return pattern.

Here, we check each condition, and return true if its met. If we get to the end and haven’t returned anything yet, we return false.

/**
 * Is a creature magical?
 * @param  {String}  creature The type of creature
 * @param  {String}  tool     The magical tool they have, if any
 * @return {Boolean}          If true, they're magical
 */
function isMagical (creature, tool) {
	if (creature === 'unicorn') return true;
	if (creature === 'elf') return true;
	if (creature === 'gnome' && tool === 'alchemy') return true;
	if (creature === 'human' && tool === 'wand') return true;
	return false;
}

So which one should you use? Whichever one you find the easiest to read and understand.