[jquery] $(form).ajaxSubmit is not a function

Ajax Submit form with out page refresh by using jquery ajax method first include library jquery.js and jquery-form.js then create form in html:

<form action="postpage.php" method="POST" id="postForm" >

<div id="flash_success"></div>

name:
<input type="text" name="name" />
password:
<input type="password" name="pass" />
Email:
<input type="text" name="email" />

<input type="submit" name="btn" value="Submit" />
</form>

<script>
  var options = { 
        target:        '#flash_success',  // your response show in this ID
        beforeSubmit:  callValidationFunction,
        success:       YourResponseFunction  
    };
    // bind to the form's submit event
        jQuery('#postForm').submit(function() { 
            jQuery(this).ajaxSubmit(options); 
            return false; 
        }); 


});
function callValidationFunction()
{
 //  validation code for your form HERE
}

function YourResponseFunction(responseText, statusText, xhr, $form)
{
    if(responseText=='success')
    {
        $('#flash_success').html('Your Success Message Here!!!');
        $('body,html').animate({scrollTop: 0}, 800);

    }else
    {
        $('#flash_success').html('Error Msg Here');

    }
}
</script>