fixup! ✨(dashboard) update javascript language switcher and add docs

src/dashboard/dashboard/static/dashboard/js/common.js

@@ -1,7 +1,39 @@
-const language_selectors = document.querySelectorAll(".fr-translate__language")
+/**
+ * Common JavaScript used in dashboard project
+ */
 
-language_selectors.forEach(el => el.addEventListener("click", event => {
-    console.log(language_selectors)
-    document.cookie = "django_language=" + el.lang + ";Path=\"/django-dsfr\";SameSite=Strict"
-    window.location.reload()
-}));
+'use strict';
+
+const app = window.app = {
+    /** ### CALL FUNCTIONS ###*/
+    init: function () {
+        this.languageSwitcher();
+    },
+
+    /** ### FUNCTIONS ###*/
+
+    /**
+     * Language switcher
+     * Sets django_language cookie, with the current language choice chosen by the user.
+     */
+    languageSwitcher: function () {
+        const language_selectors = document.querySelectorAll(".fr-translate__language")
+
+        language_selectors.forEach(el => el.addEventListener("click", event => {
+            document.cookie = "django_language=" + el.lang + ";Path=\"/django-dsfr\";SameSite=Strict"
+            window.location.reload()
+        }));
+    }
+}
+
+
+/**
+ *
+ * Wait for DOM ready and init() the app
+ *
+ */
+document.onreadystatechange = function () {
+    if (document.readyState === "interactive") {
+        app.init();
+    }
+}

src/dashboard/templates/blocks/language_selector.html

@@ -1,4 +1,9 @@
 {% load i18n %}
+
+{% comment %}
+The language selector need languageSwitcher() js function (in js/common.js) 
+{% endcomment %}
+
 <nav role="navigation" class="fr-translate fr-nav">
   {% get_current_language as LANGUAGE_CODE %}
   {% get_available_languages as LANGUAGES %}