The error is Parsing error: Cannot read property 'map' of undefined
I set up a new file just to reproduce the error:
export default () => {
let something: [string, boolean]
something = ['something', true];
}
am i missing something? all other types seem to work fine.
The Problem
The problem is when you created the tuple type [string, boolean] this is a new way to declare types with arrays introduced in Typescript 4.0 called Labeled Tuple Types.
The Solution
Upgrade your react-scripts to v4 (Here is the issue on their github). If you are using yarn use the command yarn upgrade react-scripts@4.0.1. With npm should be something similar, you can try npm install react-scripts@4.0.1
If i right understand you, here is your solution (you don't have to create a let in order to register the types, but directly in the function specify which types it will return)
// main.ts
export default (): [string, boolean] => {
return ["something", true];
};
And if you need to call this code, you just create such a component(example):
import foo from "./main.ts"
const App = () => {
return (
<div>
{foo().map(el =>
<div>
{el}
</div>
)}
</div>
)
};
Indeed it appears that the issue is with using the let keyword.
I was experiencing this when converting to TS after using let in just JavaScript a bunch of times without a hitch, but changing to const fixed it down the line.
Here are some intricacies between let and const detailed on the TypeScript website: https://www.typescriptlang.org/docs/handbook/variable-declarations.html#let-vs-const