I would like to use javascript to insert a default value into an html
form from the url.  I know how to submit the form, but need to know how to grab
the value from the url and insert it as a default value and
display it in the form.

this is an example url: www.google.com/index.html?email=gooogle@gmail.com

the value google@gmail.com should show up in the form in the email field

Hello dswilder-ga

Thank-you for your question.

The easiest way to achieve this is to look for the string ?email= in
the URL.  This can be done using "document.URL.indexOf" which returns
the position of the string ?email= in the URL if it exists or -1 if it
does not.

Once we know where the string ?email= exists in the URL we can simply
take the section of the URL we require using "document.URL.substring"
and place this value in the form element we desire.

In summary a form using this plan of action would look something like this:

<form name="test">

<script>
// see if there is a ? in the url
var is_q = document.URL.indexOf('?email=');

// check the ? is there
if (is_q != -1)
{ 
// write out the form box with the information after the ? in the box
document.write("<input type=\"test\" name=\"textbox\"
value='"+document.URL.substring(is_q+7, document.URL.length)+"' />");
}
else {
document.write("<input type=\"test\" name=\"textbox\" value='No email
address given' />");
};

</script>

</form>

To try this out simply paste everything from the <form> to </form>
tags into a blank HTML document.

Hopefully it should be a simple task from here to adapt this to your
page.  Should you require any further information on this subject
please do not hesitate to ask for clarification.

If you need other solution you can write :P