Update backup.js

js/backup.js

@@ -1,41 +1,49 @@
 import { restoreCache, todoCache } from './dbCache.js';
 
-/**NEW
+/**
  * export data from persitence
  * @returns void - calls saveDataFile()
  */
 export function backupData() {
-   // get all todo records
+   // get all todo records as a string
    const jsonData = JSON.stringify(Array.from(todoCache.entries()));
+   // create a dummy anchor element
    const link = document.createElement("a");
+   // create the file blob from the data
    const file = new Blob([jsonData], { type: 'application/json' });
+   // create a file url 
    link.href = URL.createObjectURL(file);
+   // force the link to down load as file name 'backup.json'
    link.download = "backup.json";
+   // stimulate the anchor click event
    link.click();
+   // cleanup the url object (file)
    URL.revokeObjectURL(link.href);
 }
 
 /**
  * Restore data
- *
- * @export
  */
 export function restoreData() {
 
    /** @type {HTMLElement | HTMLInputElement | null} */
    const fileload = document.getElementById('fileload');
-   const fileloadInput = /** @type {HTMLInputElement} */  (fileload) // type coersion
+   // inline type cast (coersion)
+   const fileloadInput = /** @type {HTMLInputElement} */ (fileload)
+   // simulate a user click event 
    fileloadInput.click();
-   fileloadInput.addEventListener('change', function () {
-
+   // handle user action (file select)
+   fileloadInput.addEventListener('change', function () {     
       /** @type {FileReader} */
       const reader = new FileReader();
       reader.onload = function () {
-         console.log('backup -> restoring')
+         // inline type cast
          restoreCache(/**@type{string}*/ (reader.result));
+         // refresh the app to see the restored data
          window.location.reload();
       };
-      if( fileload && fileloadInput.files ) {
+      // read the first selected json file
+      if ( fileload && fileloadInput.files ) {
          reader.readAsText(fileloadInput.files[0]);
       }
    });