没为someNode赋值过
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
<title>test for javascript</title>
<script src="script/jquery-1.9.1"></script>
<script type="text/javascript">
if(someNode.nodeType == 1){
alert("Node is an element.");
}else{
alert("Anything else ?");
}
alert("Am i OK?");
</script>
</head>
<body>
<p id="a">每个人都一样,偶尔会突发奇想!</p>
<p>
<script type="text/javascript">
var someNode=document.getElementById('a');
if(someNode.nodeType == 1){
alert("Node is an element.");
}else{
alert("Anything else ?");
}
</script>
</p>
<p>
<script type="text/javascript">
document.write("isn't it right?!");
</script>
</p>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
<title>test for javascript</title>
<script src="script/jquery-1.9.1"></script>
<script type="text/javascript">
if(someNode.nodeType == 1){
alert("Node is an element.");
}else{
alert("Anything else ?");
}
alert("Am i OK?");
</script>
</head>
<body>
<p id="a">每个人都一样,偶尔会突发奇想!</p>
<p>
<script type="text/javascript">
var someNode=document.getElementById('a');
if(someNode.nodeType == 1){
alert("Node is an element.");
}else{
alert("Anything else ?");
}
</script>
</p>
<p>
<script type="text/javascript">
document.write("isn't it right?!");
</script>
</p>
</body>
</html>
<p id="a">每个人都一样,偶尔会突发奇想!</p> // 给页面元素加上idvar someNode=document.getElementById('a');//通过id获取元素
这样就不会出现someNode is not defined