The animation only works with the first click of the button

I want to create simple text animation. When i click a button, text shifts from fully transparent to fully visible and reverts to transparent. I wrote code that does the animation but only once. The animation doesn’t work anymore every time when i click the button:

function animation() {
  $("span").removeClass("opacity-effect");
  $("span").addClass("opacity-effect");
}
span{
  opacity: 0;
}

.opacity-effect {
  animation-name: animate-opacity-effect;
  animation-duration: 1400ms;
  animation-fill-mode: forwards;
  opacity: 0;

}

@keyframes animate-opacity-effect {
  0% {
    opacity: 0;
  }
  50% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<span>Hello World!</span>
<button onClick="animation()">
   Start animation
</button>

Answer

The animation does not repeat, because for animation to start CSS requires a frame when there was no class.

So, to solve this, you should delay adding class to the next frame

function animation() {
  $("span").removeClass("opacity-effect");
  requestAnimationFrame(()=>{
    $("span").addClass("opacity-effect");
  });
}