Install Dart Code Extension for Visual Studio Code
There are many complex IDE(s) that support Dart by plugins, such as Android Studio, IntelliJ IDEA, Visual Studio Code, etc. It depends on your purpose to choose the right IDE. If you just want to learn the Dart language, Visual Studio Code is a good choice, because it is a powerful, lightweight and free IDE.
Note: If you want to learn Dart and furthermore, build a Flutter app written in the Dart language, you should use Android Studio. Dart, Flutter, and Android Studio are all created by Google, so there will be better support.
Open Visual Studio Code, then press the Extensions icon (or press Ctrl+Shift+X), and find extension(s) with the keyword "dart" as illustrated below. You will see the Dart Code Extension appear in the first position in the results. Now, press "Install" for installation.