I think the threshold of when Typescript starts being helpful is reached very quickly. Because there's always some schema in code, yes you can assign any value in JS, but then you have to remember it and account it in other code etc. There's always some schema, you just have to keep it in your head. And with TS I can offload it to the code/IDE to help me. I want to make decision about shape of an object in the moment I'm creating that abstraction or when I'm looking specifically at it deciding if it needs to be changed. I don't want to be forced to remember all those decisions all the time. If some prototype code or script is couple of screens long, sure you can easily fit it in your head and maybe you don't need additional assistance, but when it grows larger, pretty quickly it's very nice to separate process of thinking over shape of objects and process of using them.