javascript sum up selected element data value and deduct when unselect

I have 3 div which are item1, item2, and item3.

item1 with <data-price="10">， item1 with <data-price="20">， item1 with <data-price="30">

What I’m trying to do is when selected the item, it will get the item’s <data-price> and sum up, while if unselect the selected item, it will remove/deduct the <data-price>.

But my code result only shows the selected item instead of summing up.

This is my HTML code:

<div id="container2">
  <div class="row">
    <div class="col-md-3"><div id="item1" class="select_itm" data-item="1" data-price="10">Item 1 [Price = 10]</div></div>
    <div class="col-md-3"><div id="item2" class="select_itm" data-item="2" data-price="20">Item 2 [Price = 20]</div></div>
    <div class="col-md-3"><div id="item3" class="select_itm" data-item="3" data-price="30">Item 3 [Price = 30]</div></div>
  </div>
</div>
<br>
<br>
<div>
  <p>Total Price: <span id="display">0</span></p>
</div>

This is my Javascript code:

$(document).ready(function() {
  var image_selected = new Array();
  $('#container2').on('click', ".select_itm", function () {
    var aa = $(this)
    if (!aa.is('.checked')){
      aa.addClass('checked'); 
      var myprice = this.getAttribute('data-price');
      image_selected.push(myprice);
    } else {
      aa.removeClass('checked');
      var myprice=this.getAttribute('data-price');
      var index = image_selected.indexOf(myprice);
      if (index > -1) {
        image_selected.splice(index, 1);
      }
    }
    var price = 0;
    price += image_selected;
    $('#display').html(price);
  });
});

Answer

Simple way is to use checked class to loop through the checked elements

• Also is('.checked') may work but is(':checked') works with inputs checkbox/radio and to check for classes you can use if($(selector).hasClass('checked')) checked here can be any class you need to check for

$(document).ready(function() {
  $('#container2').on('click', ".select_itm", function () {
    var aa = $(this), price = 0;
    aa.toggleClass('checked');                   // toggle the class checked on click
    $(".select_itm.checked").each(function(){    // loop through the checked items
      price += parseInt($(this).data('price'));  // get total price of checked items
    });
    $('#display').html(price);  
  });
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="container2">
<div class="row">
    <div class="col-md-3"><div id="item1" class="select_itm" data-item="1" data-price="10">Item 1 [Price = 10]</div></div>
    <div class="col-md-3"><div id="item2" class="select_itm" data-item="2" data-price="20">Item 2 [Price = 20]</div></div>
    <div class="col-md-3"><div id="item3" class="select_itm" data-item="3" data-price="30">Item 3 [Price = 30]</div></div>
</div>
</div>
<br>
<br>
<div>
        <p>Total Price: <span id="display">0</span></p>
</div>

Note: The parseInt() function parses a string argument and returns an integer with parseInt 1 + 1 = 2 without it "1" + "1" = "11" .. So keep this in mind