add_and_remove_rows.js

 let buttons = `<button type="button" class="btn btn-warning lessFields"><span class="glyphicon glyphicon-minus"></span></button>
       <button type="button" class="btn moreFields"><span class="glyphicon glyphicon-plus"></span></button>`;
                                                                                                     
 prefillFields();
 bindMoreFieldsClickHandler();

 function bindMoreFieldsClickHandler() {
     $(".moreFields").click(function() {                                                                 
         console.log("on click moreFields");                                                             
         // TODO: refactor to permit more than 10 filters                                                
         var step = parseInt($(".moreFields").parent().get(0).id.slice(-1)[0]);                          
         addNewField(step + 1);                                                                          
         this.remove();
         bindMoreFieldsClickHandler();
     });  
 }                                                                                       
                                                                                                     
 $(".lessFields").click(function() {                                                                 
     var step = parseInt($(".lessFields").parent().get(0).id.slice(-1)[0]) - 1;                      
     $(".lessFields").parent().remove();                                                             
     $(`.group${step}`).append(buttons);                                                             
 });                                                                                                 
                                                                                                     
 function addNewField(count) {                                                                       
     var html = `<div class="row" id="group${count}">                                                
       <input autocomplete="off" type="text" class="form-control fieldKey" name="field${count}" placeholder="Instance Feature"       required>
       <select class="form-control comparator" name="comparator${count}" required>                   
         <option value="==">=</option>                                                               
         <option value="!=" >!=</option>                                                             
         <option value="<">&lt;</option>                                                             
         <option value="<=">&lt;=</option>                                                           
         <option value=">">&gt;</option>                                                             
         <option value=">=">&gt;=</option>                                                           
       </select>                                                                                     
       <input autocomplete="off" type="text" class="form-control fieldValue" name="value${count}" required>`
     html = html + buttons + "</div>"                                                                
     $(".statsFormFields").append(html);                                                             
     initializeTypeahead(count);                                                                     
 }