refactored javascript to ES6 classes (#759)

assets/js/KimaiPlugin.js

@@ -0,0 +1,53 @@
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/*!
+ * [KIMAI] KimaiPlugin: base class for all plugins
+ */
+
+import KimaiContainer from "./KimaiContainer";
+
+export default class KimaiPlugin {
+
+    /**
+     * Overwrite this method to initialize your plugin.
+     *
+     * It is called AFTER setContainer() and AFTER DOMContentLoaded was fired.
+     * You don't have access to the container before this method!
+     */
+    init() {
+    }
+
+    /**
+     * If you return an ID, you indicate that your plugin can be used by other plugins.
+     *
+     * @returns {string|null}
+     */
+    getId() {
+        return null;
+    }
+
+    /**
+     * @param {KimaiContainer} core
+     */
+    setContainer(core) {
+        if (!(core instanceof KimaiContainer)) {
+            throw new Error('Plugin was given an invalid KimaiContainer');
+        }
+        this._core = core;
+    }
+
+    /**
+     * This function returns null, if xou call it BEFORE init().
+     *
+     * @returns {KimaiContainer}
+     */
+    getContainer() {
+        return this._core;
+    }
+
+}