$('input.number').each(function () {
       $(this).keypress(function(e){

           if(e.keyCode == '46' || e.charCode == '46'){

             if(document.selection){

                   var range = document.selection.createRange();

                   range.text = ',';

             }else if(this.selectionStart || this.selectionStart == '0'){

                   var start = this.selectionStart;
                   var end = this.selectionEnd;

                   $(this).val($(this).val().substring(0, start) + ','
                    + $(this).val().substring(end, $(this).val().length));

                  this.selectionStart = start + 1;
                   this.selectionEnd = start +1;
               }else{

                   $(this).val($(this).val() + ',');
               }
               return false;
           }
       });
   });

<input type="text" class="number"/>

<input class="number" type="number" lang="es-ar">