영상
개념
<!DOCTYPE html>
<html lang="ko">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>onclick</title>
</head>
<body>
이름: <input type="text" id="user">
<input type="button" onclick="checkNotEmpty()" value="확인">
<script>
function checkNotEmpty() {
let field = document.getElementById('user');
if (field.value.length == 0) {
alert("필드가 비어있네요!");
field.focus();
}
}
</script>
</body>
</html>
Java
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