<!DOCTYPE html>
<html>
<body>
Full name: <input type="text" id="txtFullName"
name="FirstName" value="Vikas Ahlawat">
</body>
</html>
There are following ways to access the value of the above textbox:
var name = document.getElementById('txtFullName').value;
alert(name);
or:
we can use the old way:
document.forms[0].mybutton.
var name = document.forms[0].FirstName.value;
alert(name);
Note: This uses the "name" attribute of the element to locate it.