I'm not a TypeScript user (I've tried and run in to my own issues), yet I do see the value in Types in code.

Certainly during development with introspect into the method I want to call which helps me make sure I'm using the arguments correctly.

JSDoc, in VSCode, lets me benefit from these type feature without actually jumping all the way into TypeScript and it lets me keep my code as JavaScript and it's just better documentation.

This post is a good primer on how to use JSDoc and how you can use it in a structured way around your code.

JSDoc provides type information as comments in JavaScript, so in that sense it is more similar to Flow than TypeScript. The difference is that JSDoc comments are standard JavaScript comments. So, no need for a build step to transpile to JavaScript or a plugin to strip the comments out like Flow.

When VSCode picks up on the type definitions in my code, it definitely makes coding just that little bit easier.

Source: medium.com