JavaScript programming in an editor such as Visual Studio Code typically involves a lot of manual text editing, with the occasional copy-paste keyboard shortcuts or multi-cursor changes.
Code assists such as refactorings, code actions, and quick fixes are another tool in this repertoire. You can use code assists to make higher-level language-aware changes, e.g., you can extract an expression and all of its occurrences into a variable. When you make such changes manually, it can be time-consuming, and you risk making mistakes.
The JavaScript Assistant now contains 85 refactorings from many different categories. Check out the blog post for an overview: