Type 'string[]' cannot be used as an index type. Error in typescript but works in javascript console

Question

So the following works fine when I put in break point in the code and run the following: [browser console]

but I get Type 'string[]' cannot be used as an index type when I try to use in typescript.

Answer 1

JavaScript will let you do stupid things and won't tell you it doesn't make sense. But typescript will warn you. It's much more strict about writing coherent code. You effectively did this:

[1][[0]] // 1