index.html
<!DOCTYPE html>
<html>
<body>
<label id="count">1</label>
<br>
<button id="nextBt">+</button>
<button id="prevBt">-</button>
<script>
var timer;
elem("nextBt").onmousedown = nextKeydown;
elem("nextBt").onmouseup = nextKeyup;
elem("prevBt").onmousedown = prevKeydown;
elem("prevBt").onmouseup = prevKeyup;
function elem(id) {
return document.getElementById(id);
}
function nextKeydown() {
timer = setInterval(function() { setCount(1) }, 100);
}
function nextKeyup() {
clearInterval(timer);
}
function prevKeydown() {
timer = setInterval(function() { setCount(-1) }, 100);
}
function prevKeyup() {
clearInterval(timer);
}
function setCount(num) {
elem("count").textContent = parseInt(elem("count").textContent) + num;
}
</script>
</body>
</html>
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