How to manipulate Get query?

I have the following form from http://regain.sourceforge.net/:

<form name="search" action="search.jsp" method="get">
        <p class="searchinput">
          <b>Suchen nach: </b>
          <input name="query" size="30"/>
          <select name="order" size="1" ><option selected value="relevance_desc">Relevanz</option><option value="last-modified_asc">Dokumentendatum aufsteigend</option><option value="last-modified_desc">Dokumentendatum absteigend</option</select>

          <input type="submit" v开发者_如何学Calue="Suchen"/>
         </p>
      </form>

the search form works fine. The URL looks like the following: http://localhost:8080/regain/search.jsp?query=queryfieldvalue&order=relevance_desc

Now I want to add a checkbox to manipulate the value of the input field query. If the checkbox is checked then the query value should look like filename:"queryfieldvalue"

http://localhost:8080/regain/search.jsp?query=filename%3A%22queryfieldvalue%22&order=relevance_desc

What's the best way to do this? Javascript? Do you have a short example for me because I'm really new to javascript.

Thanks a lot in advance.

one way with pure javascript (without jquery) would be

<script type="text/javascript">
function handler()
{
    var check = document.getElementById('check');
    var query = document.getElementsByName('query')[0];
    if(check.checked)
    {
        query.value = "filename:\"" + query.value + "\"";
    }
    else
    {
        query.value = query.value.replace(/^filename:"/, "").replace(/"$/, "");
    }
}
</script>

<form>
    <input type="text" name="query" />
    <input type="checkbox" id="check" onclick="handler()" />box
</form>

it should more or less work, it would be safer if you give query input field an id and then reference it by id, not name

if you use jQuery, something like this should do:

 <input type="checkbox" id="chkQuery">Pass queryfield</input>

<script>
$(document).ready(function{}
    $("#chkQuery").click(function(){
        if ($(this).is(':checked')) 
            $("input[name='query']").val("filename:queryfieldvalue");
        else
            $("input[name='query']").val("queryfieldvalue");
    });
});
</script>