Error in event of onSubmit when validate the empty text box

I am implementing a form in html and check empty text boxes on onSubm开发者_开发技巧it event of form. In my JavaScript code I returns false but the form is still submit and redirect to new URL. What goes wrong in this code?

function checkBlank(form)
{
    var returnvar=true;
    if(form.driver.value=="")
    {
        alert("You can't left  text box Driver as blank.. ");
        driver.focus();
        returnvar=false;
    }       
    return returnvar
}


 <form name="form1" action="/Assignment6/DataBaseServlet"  onSubmit="return checkBlank(form1);" method="post">

You changed your variable names

returnvar
returnval

and the onsubmit line

return checkBlank(form1);

should use this and not form1

return checkBlank(this);

Also driver is not defined.

driver.focus();

It should be referenced with the form

form.driver.focus();

Your entire function can be:

function checkBlank(form) {
  return form.driver.value == "";
}

If you the message isn't required. Or perhaps:

function checkBlank(form) {
  if (!form.driver.value) {
    alert("Please enter a value in the driver field");
    return false;
  }
}

But you may want slightly more robust validation as that will allow a string of one or more spaces.

Hi its because of action tag . I just change my code lke this and it's working fine.enter code here

 function checkBlank(form)
  {
var returnval=true;
form.action="/Assignment_8/";
if(form.driver.value=="")
    {
    alert("You can't left  text box Driver as blank ");

    driver.focus();     
    returnval= false;
    }
if(form.url.value=="")
{
alert("You can't left  text box url as blank ");
form.url.focus();
returnval= false;
}
if(form.username.value=="")
{
alert("You can't left  text box username as blank ");
form.username.focus();
returnval= false;
}
if(form.password.value=="")
{
alert("You can't left  text box password as blank ");
form.password.focus();
returnval= false;
}
if(form.query.value=="")
{
alert("You can't left  text box query as blank ");
form.query.focus();
returnval= false;
}
if(returnval){
    form.action="/Assignment_8/database.jsp";
   }
    return true;
}
 //and form tag is..
   <form name=form1  method="post" onsubmit="return checkBlank(form1)">