https://www.tac-mobilites.fr/themes/custom/explore/js/header-height.js?tm8i2m

1(function (Drupal, once) {
2  'use strict';
3
4  Drupal.behaviors.headerHeight = {
5    onceName: 'headerHeight',
6    selector: '.site-header',
7    attach(context) {
8      // Fixed version.
9      once(this.onceName, document.querySelectorAll(this.selector), context).forEach(element => {
10        let headerHeight = element.offsetHeight;
11        document.documentElement.style.setProperty('--rd-site-header-height', headerHeight + 'px');
12      });
13    },
14    detach: function detach(context, settings, trigger) {
15      if (trigger === "unload") {
16        once.remove(this.onceName, context.querySelectorAll(this.selector));
17      }
18    },
19  };
20})(Drupal, once);