How to validate multiselect field on form submit

[talamalel]

I can't validate the multiselect on my form. I'm using livevalidation plugin for javascript like so, but it doesn't validate the field:\[code\]var features_select = new LiveValidation( "features_select", { validMessage: "Correct", onlyOnSubmit: true } );features_select.add( Validate.Custom, { against: function(value,args){ var valid = false; for(var i = 0; i < document.getElementById('features_select').options.length; i++) { if(document.getElementById('features_select').options.selected) { valid = true; break; } } return valid; }, failureMessage: "Select something"});\[/code\]Here I'm trying to use a custom validation rule ( http://livevalidation.com/documentation#ValidateCustom ) by cheking if the multiselect field had anything selected. Because Validation.Presence doesn't work on select as it seems. If not then livevalidation should display the failureMessage and don't submit the form.This is my html form multiselect field:\[code\]<select id="features_select" name="features_select[]" multiple="multiple"> <option value="http://stackoverflow.com/questions/15603045/Airbags">Airbags</option> <option value="http://stackoverflow.com/questions/15603045/Sunroof">Sunroof</option> <option value="http://stackoverflow.com/questions/15603045/AC">A/C</option> <option value="http://stackoverflow.com/questions/15603045/DVD">DVD player</option> <!-- and so on --></select>\[/code\]