simple-event-handlers.js

document.querySelectorAll('.button').forEach(function(item) {
    // Add on mouseenter
    item.addEventListener('mouseenter', function(e) {
        calculateAngle(e, this.querySelector('span'), this);
    });
    // Add on mousemove
    item.addEventListener('mousemove', function(e) {
        calculateAngle(e, this.querySelector('span'), this);
    });
    // Reset everything on mouse leave
    item.addEventListener('mouseleave', function(e) {
        let dropShadowColor = `rgba(0, 0, 0, 0.3)`
        if(item.getAttribute('data-filter-color') !== null) {
            dropShadowColor = item.getAttribute('data-filter-color')
        }
        item.querySelector('span').style.transform = `rotateY(0deg) rotateX(0deg) scale(1)`;
        item.querySelector('span').style.filter = `drop-shadow(0 10px 15px ${dropShadowColor})`;
    });
})