Frontend Mentor - Age calculator app solution

This is a solution to the Age calculator app challenge on Frontend Mentor. Frontend Mentor challenges help you improve your coding skills by building realistic projects.

Table of contents

• Overview
  • The challenge
  • Screenshot
  • Links
• My process
  • Built with
  • What I learned
  • Useful resources
• Author

Overview

The challenge

Users should be able to:

• View an age in years, months, and days after submitting a valid date through the form
• Receive validation errors if:
  • Any field is empty when the form is submitted
  • The day number is not between 1-31
  • The month number is not between 1-12
  • The year is in the future
  • The date is invalid e.g. 31/04/1991 (there are 30 days in April)
• View the optimal layout for the interface depending on their device's screen size
• See hover and focus states for all interactive elements on the page
• Bonus: See the age numbers animate to their final number when the form is submitted

Screenshot

Links

• Solution URL: Available on github pages

My process

Built with

• Semantic HTML5 markup
• CSS
• JavaScript

What I learned

I really had a lot of fun with animating the numbers when displaying the result on the screen; it was a tricky but rewarding exercise.

Animating the numbers counting up:

function animateValue(obj, start, end, animationDuration) {
    let startingTime = null;

    const step = (currentTime) => { // animate each 'frame'
        if (!startingTime) startingTime = currentTime;
        const progress = Math.min((currentTime - startingTime) / animationDuration, 1);
        obj.textContent = Math.floor(progress * (end - start) + start);
        if (progress < 1) {
            window.requestAnimationFrame(step);
        }
    };

    window.requestAnimationFrame(step); // starting the animation
}

The window.requestAnimationFrame(step) really came in handy here!

Putting the animation together:

async function displayResult() {
    animateValue(document.querySelector('#no-of-years'), 0, years, 500);
    await sleep(500);
    animateValue(document.querySelector('#no-of-months'), 0, months, 500);
    await sleep(500);
    animateValue(document.querySelector('#no-of-days'), 0, days, 500);
}

sleep() function:

function sleep(milliseconds) {
    return new Promise(resolve => setTimeout(resolve, milliseconds));
}

I used the await keyword in the displayResult() function since promises are asynchronous, so i had to make sure the carry out the promise in the sleep() function first before animating the next number. This enabled me to create a time delay.

Overall, this was a really interesting and fun project!

Useful resources

• W3schools - Helped me with styling certain elements
• MDN web docs - Helped me a lot with the fetch API and a great general reference
• Sitepoint blogs - explained JavaScript concepts really well

Author

• Frontend Mentor - @SushiOnToast
• CodePen - @SushiOnToast
• CodeWars - @SushiOnToast