getElementById
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>DOM</title>
<script type="text/javascript">
function btn_click( ){
//dom 모를때
//var txt = document.frm.name.value;
//alert(txt);
//dom쓸수있을떄
//var irum = document.getElementById(irum);
//var irum = document.getElementById("irum").value;
//var hakbun = document.getElementById("hakbun").value;
//var result = document.getElementById("result");
//result.innerHTML = '안녕 ' + irum + "님";
/* var inlist = document.getElementsByTagName('input');
for(var i = 0; i<inlist.length;i++){
if(inlist.item(i).type == 'text' && inlist.item(i).value==''){
alert('입력하세요');
return;
}
} */
/* var lbl = document.getElementById('label');
var children = lbl.childNodes;
alert(children.length); */
var lbl = document.getElementById('label');
var children = lbl.childNodes;
for(var i = 0; i<children.length;i++){
if( children.item(i).value==''){
alert('필수사항 입력하세요');
return;
}
}
//입력 필수 사항이라고 체크하여 메시지창 띄우기
}
</script>
</head>
<body>
<form id="" name="frm" action="">
<label id="label">
이름 :
<input type="text" name = "irum" id="irum" size="10" /> <br/>
학과 :
<input type="text" name = "dept" id="dept" size="10" /> <br/>
학교 :
<input type="text" name = "school" id="school" size="10" /> <br/>
</label>
<input type = "button" value = "눌러" onclick = "btn_click( )"/>
<div id = "result"/>
</form>
</body>
</html>