<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="initial-scale=1.0">
<title>要素の取得と操作2～属性・スタイルの設定</title>
<style>
.a{
width:10em;
height:3em;
background:pink;
border:3px dotted gold;
}
</style>
</head>
<body>
<h1 class="title">要素の取得と操作2～属性・スタイルの設定</h1>
<div>
<div id="no_display">見えなくなる</div>
<div id="test">test</div>
<div id="nostyle">nostyle</div>
<div id="noclass">noclass</div>
</div>
<script>
document.getElementsByTagName('body')[0].style.background = '';
document.getElementsByClassName('title')[0].style.color = '';
document.getElementsByTagName('div')[0].style.display = '';
document.getElementById('no_display').style.display = '';
document.getElementById('test').style = 'width:10em;height:3em;';
document.getElementById('nostyle').setAttribute('' , 'width:10em;height:3em;');
document.getElementById('noclass').setAttribute('' , '');
</script>
</body>
</html>