Jquery - Change value from option value

Answer 1

You can use callback function of .attr() to modify existing value:

$('#ListSujet option').attr('value',function(i,o){
    return  o.substring(0, o.indexOf(','))
});

Working Snippet:

$('#ListSujet option').attr('value',function(i,o){
   return  o.substring(0, o.indexOf(','))
});

$("#ListSujet").on("change",function(){
  console.log($(this).val());
});