How to make get for drupal behaviors to run only once?

Question

Drupal.behaviors.js_mod = {
attach: function (context, settings) {
     //$('body', context).append(chart);
    // $( '#drupal-myradar', context ).once
     $.get( "/web/js/mod", function( data ) {
        console.log(data);
      });
}

    }
})(jQuery, Drupal, drupalSettings); 

Essentially this code is running multiple times while grabbing information from my controller code. I only want this to print out once to the console when the page is loaded.

Answer 1

This works as designed. Behaviors attach runs multiple times, but the scope provided in context changes. So check if the element is in context and apply once() to get the element only one time:

 Drupal.behaviors.js_mod = {
    attach: function attach(context, settings) {
      var $myradar = $(context).find('#drupal-myradar').once('js_mod');
      if ($myradar.length) {
        ...

Answer 2

If your script is high-level, which is most likely, then only run it when the context is equal to the document. I found this trick in the autologout module and use it almost everywhere now:

Drupal.behaviors.dosomething = {
  attach: function attach(context, settings) {
    if (context !== document) {
        return;
    }
    // Do stuff here but still use .once when attaching behaviors.
  ...

Answer 3

That would do :

(function($, Drupal, drupalSettings) {    
    let onlyOnce;
    Drupal.behaviors.js_mod = {
      attach: function (context, settings) {
          if (!onlyOnce) {
            onlyOnce = true;
            //$('body', context).append(chart);
            // $( '#drupal-myradar', context ).once
            $.get( "/web/js/mod", function( data ) {
              console.log(data);
            });
          }
       }    
     }
})(jQuery, Drupal, drupalSettings);