I started working with TypeScript over vanilla JS a year or so ago. It's completely changed the way I work. Having autocomplete, pointing out silly errors (forgetting to return a value, forgetting to set a prop on a React component, forgetting to add a member to an object) before I refresh the page, and being able to pick up old code without having to reread through it to figure out what the hell it actually spits back out is a godsend. The latter has sped up my productivity significantly; being able to get the output from a library, hover over the variable, and see the exact shape of the output saves an incredible amount of time when doing mundane day-to-day tasks.