1) Code refactoring. TypeScript paves the way here. I once refactored some UI code from 1400 lines of typed jQuery to 700 lines of React. I didn't test or even run my code, but I pushed it to a branch and my co-worker pulled it and told me it worked first try and passed all QA. It would have taken much longer to refactor with plain JS, and likely would not have worked first try. From completion in JS, to completion in templates (JSX) to completion in the styles (CSS-in-JS), the refactoring was a total breeze. I have never had such a good time doing major JS refactoring until I used TypeScript.
2) Communication: more than anything, types allow cross-developer communication with nothing but code. Interfaces tell other people what you intend (without them having to open a separate test file for example). It saves time in understanding code. This is important, for future devs coming onto a project (and previous devs leaving).
I think you'll appreciate TS more when you consider those aspects.
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A few points you haven't covered:
1) Code refactoring. TypeScript paves the way here. I once refactored some UI code from 1400 lines of typed jQuery to 700 lines of React. I didn't test or even run my code, but I pushed it to a branch and my co-worker pulled it and told me it worked first try and passed all QA. It would have taken much longer to refactor with plain JS, and likely would not have worked first try. From completion in JS, to completion in templates (JSX) to completion in the styles (CSS-in-JS), the refactoring was a total breeze. I have never had such a good time doing major JS refactoring until I used TypeScript.
2) Communication: more than anything, types allow cross-developer communication with nothing but code. Interfaces tell other people what you intend (without them having to open a separate test file for example). It saves time in understanding code. This is important, for future devs coming onto a project (and previous devs leaving).
I think you'll appreciate TS more when you consider those aspects.