Sleep function in JavaScript

sleep.js

// ===============
// Sleep function.
// ===============

const sleep = async (seconds = 0) => {
    // Expose promise.
    return new Promise((resolve) => {
        // Set timer.
        setTimeout(() => {
            // Resolve promise.
            resolve(undefined);
            
            // Delay.
        }, seconds * 1000);
    });
};

// =====================================
// Test function: `await` function call.
// =====================================

const testFunction1 = async () => {
    // Set delay.
    const delay = 5;

    // Wait for delay.
    await sleep(delay);

    // Continue.
    console.log(`Seconds slept: ${delay}`);
};

// ========================================
// Test function: `await` variable instead.
// ========================================

const testFunction2 = async () => {
    // Set delay.
    const delay = 10;

    // Assign value.
    const zzz = sleep(delay);

    // Wait for delay.
    await zzz;

    // Continue.
    console.log(`Seconds slept: ${delay}`);
};

// ====================================
// Test function: uses `then` chaining.
// ====================================

// Test function.
const testFunction3 = () => {
    // Set delay.
    const delay = 15;

    // Wait for delay.
    sleep(delay).then(() => {
        // Continue.
        console.log(`Seconds slept: ${delay}`);
    });
};

// ====================
// Call test functions.
// ====================

// Logs after 15 seconds.
testFunction3();

// Logs after 10 seconds.
testFunction2();

// Logs after 5 seconds.
testFunction1();