Lesson 10: Local Storage & Polish

60 minutes

Ages 8-18+

Lesson Progress 10%

What You'll Learn Today

In our final lesson, you'll learn how to make your todo app remember everything even after closing the browser! We'll also add professional polish to make your app look and feel amazing.

What is Local Storage?

Local Storage is like a small filing cabinet in your browser that can save information permanently. When you close your browser and come back later, the data is still there! This is perfect for saving todo lists, user preferences, and other important information.

Learning Objectives

Implement data persistence using localStorage to save and load todos.
Handle JSON data to store complex objects in localStorage.
Add professional polish with animations, error handling, and better user experience.

Local Storage Methods

Local Storage gives us simple methods to save and retrieve data. Here are the essential ones you'll use:

localStorage.setItem(key, value) Save Data

This saves data to localStorage with a specific name (key). The data stays there until you delete it or clear browser data. Perfect for saving your todo list!

localStorage.getItem(key) Load Data

This retrieves previously saved data using its key. If no data exists with that key, it returns null (empty).

JSON.stringify(object) Convert to Text

localStorage can only save text, so we use this to convert our todo objects and arrays into text format before saving.

JSON.parse(text) Convert from Text

This converts saved text back into JavaScript objects and arrays so we can use them in our code again.

Your Final Mission: Complete Todo App

You'll complete the professional todo app by implementing localStorage and adding polish. The basic structure is provided - you'll add the persistence and finishing touches.

Pro Tip

Always wrap localStorage operations in try-catch blocks to handle errors gracefully. Some browsers might have localStorage disabled!

Step 1: Implement `saveTodos()`
Use localStorage.setItem() and JSON.stringify() to save the todos array to localStorage with the key 'todos'.
Step 2: Implement `loadTodos()`
Use localStorage.getItem() and JSON.parse() to load saved todos when the app starts. Handle the case where no saved data exists.
Step 3: Add Polish
Make sure to call saveTodos() after every change, handle empty states, and test your app by refreshing the page!

Congratulations!

You've successfully completed your first full web application with HTML, CSS, JavaScript, and data persistence. This is a real developer skill!

Take It Further

After completing this lesson, you'll have built a complete, professional todo application! Here are some ideas to make it even better:

Add the ability to edit existing tasks by double-clicking them
Include due dates for tasks and show overdue items
Add categories or tags to organize tasks better
Make your app work offline as a Progressive Web App (PWA)