where datavaluefield values checkboxlist stored?

i have checkboxlist page:

<asp:checkboxlist runat="server" id="locations" datasourceid="locationsdatasource"
   datatextfield="countryname" datavaluefield="countrycode" />

i'd loop by checkbox elements fan controlling javascript squeeze value any checked checkbox, nonetheless values don't seem accessible fan side. html cost looks this:

<table id="ctl00_content_locations" class="searchfiltercheckboxlist" cellspacing="0" cellpadding="0" border="0" style="width:235px;border-collapse:collapse;">
<tr>
    <td><input id="ctl00_content_locations_0" type="checkbox" name="ctl00$content$locations$0" /><label for="ctl00_content_locations_0">democratic commonwealth congo</label></td>
</tr><tr>
    <td><input id="ctl00_content_locations_1" type="checkbox" name="ctl00$content$locations$1" /><label for="ctl00_content_locations_1">central african republic</label></td>
</tr><tr>
    <td><input id="ctl00_content_locations_2" type="checkbox" name="ctl00$content$locations$2" /><label for="ctl00_content_locations_2">congo</label></td>
</tr><tr>
    <td><input id="ctl00_content_locations_3" type="checkbox" name="ctl00$content$locations$3" /><label for="ctl00_content_locations_3">cameroon</label></td>
</tr><tr>
    <td><input id="ctl00_content_locations_4" type="checkbox" name="ctl00$content$locations$4" /><label for="ctl00_content_locations_4">gabon</label></td>
</tr><tr>
    <td><input id="ctl00_content_locations_5" type="checkbox" name="ctl00$content$locations$5" /><label for="ctl00_content_locations_5">equatorial guinea</label></td>
</tr>

the values ("cd", "cg", "ga", etc.) nowhere found. where they? even illusory opening client, i need build checkboxlist myself controlling repeater something?