This my simple local budget App!

1. Important aspect of any robust application’s architecture.
2. Keep the units of code for a project both cleanly separated and organized.
3. Encapsulate some data into privacy and expose other data publicly.

Add event handler
Get input value
Add the new item to our data structure
Add the new item to the UI
Calculate budget
Update the UI

In JavaScript, use Closure and IIFE to make our code public and private separately.