Javascript gained a number of new features in the past years that are being used extensively these days, but which aren't included in the Javascript tutorial on w3schools.
To name a few examples:
- Prototypes
- Arrow functions
- Callbacks
- Promises
- Then
- Async and Await (<-- asynchronicity)
- Iterators and Generators (async iterators and generators)
- Modules (export, import, dynamic imports)
The Javascript tutorial would be improved and made up to date by including these topics. Especially, arrow functions, callbacks, promises, 'then' and Async/Await are used a lot these days.