jquery add new input box with click

add-new.js

//Add new section click
$('#sections').on('click', 'button',function() {
  var sectionNum = $('#sections').children().length + 1;
  // Create the snippet of html for each section
  var html = '<div class="block">';
  html += '<div class="inline form-group">';
  html += '<label>Section ' + sectionNum + '</label>';
  html += '<input class="lesson-section" id="section' + sectionNum + '">';
  html += '</div>';
  html += '<div class="inline form-group">';
  html += '<button class="addSection">+</button>';
  html += '</div>';
  html += '</div>';
  $('#sections').append(html);
  $(this).hide();
});

//clear lesson
$('#clear').click(function() {
  var firstSection = $('#sections').children().first();
  
  $('#sections').empty();
  $('#sections').append(firstSection);
  $('button').show();        

});

// insert the created lesson
$('#insert-lesson').click(function() {
  var formData = {"title": $('#lesson-title').val()};
  
  $('.lesson-section').each(function() {
    formData[$(this).attr('id')] = $(this).val();
  });
  
  console.log(formData);
  
  google.script.run
    .withSuccessHandler(function(response) {
      // close the sidebar
    })
    .insertLesson(formData);
});