h1 jQuery delay & queue sample
.container
  .element
  .element
  .element
  .element

@import url('https://fonts.googleapis.com/css?family=Roboto+Slab&display=swap');
body {
  background: #333;
  font-family: 'Roboto Slab', serif;
}
h1 {
  text-align: center;
  color: #fff;
  margin-top: 80px;
  letter-spacing: .05em;
}
button {
  display: block;
  margin: 0 auto;
}
.container {
  display: flex;
  justify-content: center;
  padding: 40px 50px 120px;
}

.element {
  width: 15vw;
  height: 15vw;
  border-radius: 50%;
  background: #FFD05C;
  margin: 16px;
  opacity: 0;
  transition: opacity 1s;
  &.is-active {
    opacity: 1;
  }
}

const element = $('.element');
const delayTime = 300;

element.each(function (i) {
  $(this).delay(i * delayTime).queue(()=> {
    $(this).addClass('is-active').dequeue();
  });
});