<!DOCTYPE html>
<html lang="ja">
<head>
<script type="text/javascript">
window.onload = () => {
// (1)イベントを設定
for (var element of document.getElementsByClassName('range')) {
element.addEventListener('input', (event) => {
// (2)ソース要素のvalueを次(隣)の要素のinnerHTMLへセット
event.srcElement.nextElementSibling.innerHTML = event.srcElement.value;
});
}
// (3)初期表示するためにイベントを起こす
for (var element of document.getElementsByClassName('range')) {
element.dispatchEvent(new Event('input'));
}
}
</script>
</head>
<body>
<div>
<label>range A</label>
<input type="range" class="range" value="50"><span></span>
</div>
<div>
<label>range B</label>
<input type="range" class="range" value="50"><span></span>
</div>
</body>
</html>