How to select/deselect all checkboxes using JavaScript

In this article, you will learn how to manage checkboxes selections using JavaScript. If there is a long list of check boxes in a form, it becomes very hectic to check each one individually, and it also looks very wired. For this, we have created three sections using HTML and kept some elements with checkboxes in each section. There is a checkbox 'Select All' with each section heading.

When the user clicks on the 'Select All' checkbox, the elements under that section will get checked. This checkbox toggles the other checkboxes.

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>How to select/deselect all checkboxes using Javascript </title>
    <style type="text/css">
            .bg_head { background-color: #003366; color: #fff;}
            .bg_element {  background-color: #99CC99;}
    </style>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
    <script type="text/javascript">
            function checkAllInCategory($b){ 
                var b = $b;
                var chkelement = 'checkdata_'+b;
                var chscl =  'ele_'+b;
                var elements = document.getElementsByClassName(chscl); 
                $selectallsch       = document.getElementById(chkelement).checked;  
                for(var i=0;i<elements.length;i++){ 
                    if($selectallsch == true ) {  
                        elements[i].checked = true
                    }
                    if($selectallsch == false ) { 
                        elements[i].checked = false
                    }
                }
            }
      </script>
  </head>
  <body>
    <table cellpadding="3" border="1">
    <?php 
        $data = array('Flowers'=>array('Rose', 'Lily', 'Sunflower'), 
                      'Animals'=>array('Cat', 'Dog', 'Rat'), 
                      'City'=>array('Delhi', 'Pune', 'Mumbai'));
       foreach($data as $key=>$category) {
    ?>
    <tr class="bg_head">
     <td><b><?php echo ucfirst($key); ?></b></td>
     <td>
     <input type="checkbox" id="checkdata_<?php echo $key; ?>" onclick="checkAllInCategory('<?php echo $key; ?>')" />
     </td>
    </tr>
    <?php
      foreach($category  as $element){
        echo '<tr class="bg_element"><td><b>'.$element.'</b></td><td>';
    ?>
    <input type="checkbox" name="<?php echo $key; ?>[]" class="ele_<?php echo $key; ?>" value="<?php echo $element; ?>" />
    <?php
       echo '</td></tr>';
      }
    } 
    ?>
    </table>
  </body>
</html>

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