Add file utility module.

assets/js/utils/file.js

@@ -0,0 +1,37 @@
+/* ----------------------------------------------------------------------------
+ * Easy!Appointments - Online Appointment Scheduler
+ *
+ * @package     EasyAppointments
+ * @author      A.Tselegidis <alextselegidis@gmail.com>
+ * @copyright   Copyright (c) Alex Tselegidis
+ * @license     https://opensource.org/licenses/GPL-3.0 - GPLv3
+ * @link        https://easyappointments.org
+ * @since       v1.5.0
+ * ---------------------------------------------------------------------------- */
+
+/**
+ * File utility.
+ *
+ * This module implements the functionality of files.
+ */
+window.App.Utils.File = (function () {
+    /**
+     * Convert a file to a base 64 string.
+     *
+     * @param {File} file
+     *
+     * @return {Promise}
+     */
+    function toBase64(file) {
+        return new Promise((resolve, reject) => {
+            const reader = new FileReader();
+            reader.readAsDataURL(file);
+            reader.onload = () => resolve(reader.result);
+            reader.onerror = (error) => reject(error);
+        });
+    }
+
+    return {
+        toBase64
+    };
+})();