I am trying to create a search form with a dropdown menu that allows visitors on a site to choose on which site to perform their search.

The dropdown menu offers a selection of sites to search.

So far, I got this far : https://biblio.brossard.ca/boite-de-recherche-test/.

Everything works great except when I use words with accented letters (é, ê, à, î, etc.) in the search box.

Here is the HTML code :

<form name="searchform" id="searchform" class="search-form" onSubmit="return dosearch();">
<div class="search-form-wrap">
<div class="selecteur">
<select name="sengines">
<option id="options" value="https://biblio.brossard.ca/?s=">Site Web</option>
<option id="options" value="https://catalogue.brossard.ca/query?q=" selected>Catalogue</option>
<option id="options" value="https://bibliothequemunicipaledebrossard.on.worldcat.org/v2/search?queryString=">Catalogue international</option>
</select></div><input type="text" name="searchterms" class="search-form-input" style="border-radius: 0 25px 25px 0; width: 70%; display: inline;" placeholder="Saisissez les termes de votre recherche."><input type="submit" name="SearchSubmit" id="searchsubmit" class="button submit-button" value="&#xf179;" />
</div>
</form>

And here is the javascript code :

<script type="text/javascript">
function dosearch() {
var sf=document.searchform;
var submitto = sf.sengines.options[sf.sengines.selectedIndex].value + escape(sf.searchterms.value);
window.location.href = submitto;
return false;
}
</script>

So, how could I make a search form in which visitors on my site can select where to perform their search from a selection in a dropdown menu and the search will work with both words with and without accented characters?

Many thanks for your help.