<!-- <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
function helloworld(){
document.write("hello world");
}
</script>
<form>
<input type="submit" onclick = helloworld()>
</form>
</body>
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<!-- <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<script>
function validateform(){
var name=document.getElementById("name").value;
var roll=document.getElementById("roll").value;
if(name==="" || roll===""){
alert("name and roll required");
return false
}
return true;
}
</script>
</head>
<body>
<form >
<label for ="name">Name</label>
<input type="txt" id="name">
<label for ="roll" >roll</label>
<input type="number" id ="roll">
<input type="submit"onclick=validateform());
</form>
</body>
</html> -->