how to get multiple checkbox values from html form

Question

I understand that I can use jQuery (how to get multiple checkbox value using jquery) to get checkbox values when there are multiple, but my checkbox inputs are inside an html form, so those jQuery solutions aren't working because none of them get the checkbox values from within a form.

I try to extract the values from the form, but it just creates a weird radio nodelist that seems to count the number of times the name of the checkboxes appears in the doc rather than the values.

function validateForm() {
  var checks = document.forms["TestForm"]["ParticipantSelection[]"];
  alert(checks);

}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.0/jquery.min.js"></script>

<form name="TestForm" action="Video1.php" method="post" onsubmit="return validateForm()">

  <table>

    <tr>
      <th><img name="<?php echo $valueindicator[0];?>" src="<?php echo $all_four_images[0];?>" height="100">
      </th>

      <th><img name="<?php echo $valueindicator[1];?>" src="<?php echo $all_four_images[1];?>" height="100">
      </th>
      <th><img name="<?php echo $valueindicator[2];?>" src="<?php echo $all_four_images[2];?>" height="100">
      </th>
    </tr>

    <tr>
      <th> <input type="checkbox" name="ParticipantSelection[]" value="image1">
      </th>

      <th><input type="checkbox" name="ParticipantSelection[]" value="image2">
      </th>

      <th><input type="checkbox" name="ParticipantSelection[]" value="image3">
      </th>
    </tr>


  </table>
  <input type="hidden" name="AnswerCondition" value="BrowserCheckAnswer">


  <button type="submit">Continue</button>

</form>

But I have no idea how to get the js to get the value of whats inside the form inputs instead of counting something else, and no idea how to access the values of the checked boxes

Solution 1

You can use jQuery .map() function to iterate through each checked checkbox input type. This will return an object with the selected checkboxes. Now, to get an array from the jQuery object we can use the .get() method like this:

Try this:

var validateForm = function() {
  var checks = $('input[type="checkbox"]:checked').map(function() {
    return $(this).val();
  }).get()
  console.log(checks);
  return false;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<form name="TestForm" action="Video1.php" method="post" onsubmit="return validateForm()">
  <table>
    <tr>
      <th> <input type="checkbox" name="ParticipantSelection[]" value="image1">
      </th>

      <th><input type="checkbox" name="ParticipantSelection[]" value="image2">
      </th>

      <th><input type="checkbox" name="ParticipantSelection[]" value="image3">
      </th>
    </tr>
  </table>
  <input type="hidden" name="AnswerCondition" value="BrowserCheckAnswer"/>
  <button type="submit">Continue</button>
</form>

Solution 2

checks is an array-like object representing all the elements with that name.

Loop over it like an array. Each member will have a value property representing the value and a checked (boolean) property that will tell you if it is checked or not.

Comments

[takendarkk]

Try using .value on something if you want its value. Similar to how you did document.forms.

[S Floyd]

hi- thanks so much for the reply! I did try this several times- it returns undefined because of the html checkbox name (which is something I need to have to post the data).

[Mahesh Singh Chouhan]

You can mark this answer as helpful, it is works for you so that it helps others as well. Thanks

[S Floyd]

hi! it definitely counted the selections, which I am thrilled about! However, checks turns out to be an Object object, but I can just use Object.values(checks) to get it out :) it does return a very weird list though which contains a bunch of stuff besides the checkbox values, making it hard to count what's inside, for example.

[S Floyd]

Hi, thanks for the quick reply! Sorry for not clarifying- I tried this several times before posting. Not sure why it didn't work, but none of the incarnations of this loop I tried worked.

[Quentin]

@SFloyd — I can't tell why they didn't work either. Try providing a minimal reproducible example

[Mahesh Singh Chouhan]

Updated answer to get selected values array from jQuery object :)

[Sagar Darekar]

You should explain what your code does, and how it fixed the problem. that would be helpfull.