如何使用Javascript打开模式？

Question

I am a student learning to code and have just started to learn javascript/jquery. I have created a RoR chess game and am currently working on the promotion move. Basically, once a Pawn piece has reached the opposite end of the board, a modal should open and give the player a selection of pieces to choose from to replace the pawn with. On the front end I have this modal that should automatically be triggered when a pawn meets the necessary conditions. I created a function is_pawn_promotion that should do so, but the modal still does not open on it's own, and now I am unsure what to do next. I am wondering if the is_pawn_promotion function is not being called properly (obviously it is not). I have tried to reorganize the location of the openModal function but to no avail. Any help would be greatly appreciated and hopefully I have provided a clear enough picture of what is going on.

Here is the JS file containing the is_pawn_promotion . I have included the whole file which contains the openModal function I am trying to call in order to open the modal.

$( function() {
  $( ".piece" ).draggable({
    snap: ".piece-square",
    grid: [60, 60],
    containment: ".game-board",
  });


  $( ".piece-square" ).droppable({
    accept: ".piece",
    drop: function( event, ui ) {
      var x = $(event.target).data('x');
      var y = $(event.target).data('y');
      var urlUpdatePath = $('.ui-draggable-dragging').data('url');
      var is_pawn_promotion = function() {
        return $(".piece") === 'Pawn' &&
          (y === 0 || y === 7); 
      };

      var sendAJAXRequest = function(x, y, type) {
        $.ajax({
          type: 'PUT',
          url: urlUpdatePath,
          data: { piece: { x_position: x, y_position: y, piece_type: type} },
          success: function(response) {
            if(response == 'OK') {
              console.log(response);
            } else {
              alert(response);
            }
          }
        });
      };

          if (is_pawn_promotion()) {
            openModal();
            var promoSubmitButton = $(".promo-selection-submit");
            promoSubmitButton.on('click', function() {
              var type = $('.promo-selection.input[selected]').val();
              sendAJAXRequest(x, y, type);
              });
            } else { 
              sendAJAXRequest(x, y);
            }
          }
        });
    });

    var openModal = function() {

      // Change modal-state checkbox to checked
      $("#promo-modal").prop("checked", true);

        if ($("#promo-modal").is(":checked")) {
          $("body").addClass("modal-open");
        } else {
          $("body").removeClass("modal-open");
        }

      $(".modal-fade-screen, .modal-close").on("click", function() {
        $(".modal-state:checked").prop("checked", false).change();
      });

      $(".modal-inner").on("click", function(e) {
        e.stopPropagation();
      });
    };

the modal

<div class="modal">
  <input class="modal-state" id="promo-modal" type="checkbox" />
  <div class="modal-fade-screen">
    <div class="modal-inner">
      <div class="modal-close" for="promo-modal"></div>
        <div class="promo-modal-text">
          <h1>Pawn Promotion!</h1>
          <h1>Make your selection: </h1>
        </div>
        <form action="#" class="pawn-promotion">
          <div class="promo-selection-container">
            <% [Queen, Knight, Bishop, Rook].each do |piece_type| %>
              <div class="promo-selection">
                <label>
                  <%= image_tag(piece_type.new(color: current_color).piece_image) %>
                  <%= piece_type.name %>
                  <input type="radio" name="promo-piece" value="<%= piece_type.name %>">
                </label>
              </div>
            <% end %>  
          </div>
          <br/>
          <div class="promo-selection-submit">
            <input type="submit">
          </div>
        </form>
    </div>
  </div>
</div>

Answer 1

You are calling the function, before you declare it. Try changing its location.

Answer 2

I managed to find a solution on my own. The main problem was how I was defining the is_pawn_promotion function. I changed that to the following:

var is_pawn_promotion = function() {
  return ui.draggable.data('pieceType') === 'Pawn' &&
    (y === 0 || y === 7); 
};

I also had to add the data-piece-type property to the actual piece in the view like so:

<div class="piece" data-url="<%= game_piece_path(piece.game, piece)%>" data-piece-type="<%= piece.piece_type %>">
  <%= image_tag(piece.piece_image) %>
</div>

Now the modal opens when a pawn piece is in a position to be promoted.