Future JavaScript today

A second big benefit is that TypeScript allows you to use the newest ECMAScript features right now, whether you're targeting the latest version of Node.js or Internet Explorer 11 (poor soul!). This is great because it means that you don't need to wait until everything is supported in the target environment.

You can very easily configure the TypeScript compiler to generate ES3-, ES5-, ES2015-, ES2016-, ES2017-, ES2018-, ES2019-, or ESNext-compatible code.

To make this clearer, let's take an example. In TypeScript, you can create classes while transpiling your code to ES3-compliant code, even though classes were only introduced in ES2015. The TypeScript compiler only performs transformations to use language constructs that existed in that version of ECMAScript. When TypeScript does this, we often talk about down-level emit. There are many features of most recent ECMAScript versions that you can use with TypeScript while targeting ES5.