setinterval()とclearInterval()

setInterval()

<button onclick="increment()">PowerUp</button>
<script>
function increment() { x += 1 }
setInterval("increment()", 1000); /* 1000=1s */
</script>

clearInterval()

x = setInterval("increment()", 1000);
if(percentage === 100 ){
  clearInterval(x);
}