TypeScript cookbook

I just learned JavaScript, and rewriting my whole project in TypeScript from scratch sounds like starting over.

My variable definitely isn't undefined. TypeScript disagrees.

I read a setting back from localStorage and TypeScript just calls it any, so nothing checks it anymore.

My fetch call works fine at runtime, but the response comes back typed as any, so my editor can't suggest a single property on the data.

I installed a package. TypeScript can't find its types.

Interface or type? I never know.

Half my code uses an enum for status, the other half just compares plain strings against each other, and honestly I don't know anymore which one is right.

My API call returns either data or an error, and half my code has to guess which one it got.

It imports fine in the editor. Then the build fails.

I've now written the same lookup function three separate times, once for every data shape, because TypeScript won't let me share just one version of it.

I keep copying my interface and deleting fields by hand.

Somebody added a new status value. One switch statement never got updated.