Add Set The Type For A useState Hook as a React til

react/set-the-type-for-a-usestate-hook.md

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+# Set The Type For A useState Hook
+
+TypeScript can often infer the type of a `useState` hook. For instance, in the following example, TypeScript infers a type of `boolean`:
+
+```typescript
+const [open, setOpen] = React.useState(false);
+```
+
+If we have a `useState` hook that can be `null` or a string:
+
+```typescript
+const [error, setError] = React.useState(null);
+
+setError('There was an error');
+// Argument of type 'string' is not assignable
+// to parameter of type 'SetStateAction<null>'
+```
+
+then we'll get a TypeScript warning when we violate the inferred type of
+`SetStateAction<null>`.
+
+The `useState` can be appropriate typed for this situation like so:
+
+```typescript
+const [error, setError] =
+  React.useState<null | string>(null);
+```
+
+[source](https://www.carlrippon.com/typed-usestate-with-typescript/)