This tutorial shows how to build a link navigator micro-animation UI element like Stripe's.

It mixes JavaScript and CSS to transition a tooltip background behind a navigation dropdown list. The dropdown element has two events for transitions, .trigger-enter and .trigger-enter-active, while the tooltip has only an .open transition.

/* dropdown list */
.trigger-enter .dropdown {
  display: block;
}

.trigger-enter-active .dropdown {
  opacity: 1;
}

/* tooltip */
.dropdownBackground.open {
  opacity: 1;
}

Some concepts taught:

• revisioning getBoundingClientRect() which returns a DOMRect with an objects complete bounding box coordinates
• setting properties with ES6 template literals
• event delegation and order

// set the second class after a delay only if the first has not been removed
this.classList.add('trigger-enter')
setTimeout(() =>
  this.classList.contains('trigger-enter') && this.classList.add('trigger-enter-active'), 150)