Author: John Au-Yeung

Sometimes, we want to rewrite the protected routes using TypeScript and React-Router 5.

In this article, we’ll look at how to rewrite the protected routes using TypeScript and React-Router 5.

How to rewrite the protected routes using TypeScript and React-Router 5?

To rewrite the protected routes using TypeScript and React-Router 5, we can define our own prop type for our route component.

For instance, we write

import { Redirect, Route, RouteProps } from "react-router";

type ProtectedRouteProps = {
  isAuthenticated: boolean;
  authenticationPath: string;
} & RouteProps;

export default function ProtectedRoute({
  isAuthenticated,
  authenticationPath,
  ...routeProps
}: ProtectedRouteProps) {
  if (isAuthenticated) {
    return <Route {...routeProps} />;
  } else {
    return <Redirect to={{ pathname: authenticationPath }} />;
  }
}

to define the ProtectedRouteProps type that has the prop properties that we defined.

And then we combine that with RouteProps by creating an intersection type with it with &.

Then ProtectedRouteProps should have the props from both types.

And then we can use the props without TypeScript compiler errors.

Conclusion

To rewrite the protected routes using TypeScript and React-Router 5, we can define our own prop type for our route component.

Sometimes, we want to rewrite the protected routes using TypeScript and React-Router 6.

In this article, we’ll look at how to rewrite the protected routes using TypeScript and React-Router 6.

How to rewrite the protected routes using TypeScript and React-Router 6?

To rewrite the protected routes using TypeScript and React-Router 6, we can define the type for the route props ourselves.

For instance, we write

export type ProtectedRouteProps = {
  isAuthenticated: boolean;
  authenticationPath: string;
  outlet: JSX.Element;
};

export default function ProtectedRoute({
  isAuthenticated,
  authenticationPath,
  outlet,
}: ProtectedRouteProps) {
  if (isAuthenticated) {
    return outlet;
  } else {
    return <Navigate to={{ pathname: authenticationPath }} />;
  }
}

to define the ProtectedRouteProps with some properties for the ProtectedRoute component props.

Then we can destructure the props and use them in the component.

We render outlet, which has the route component if isAuthenticated is true.

Next, we can use ProtectedRoute by writing

const App = () => {
  //...
  const defaultProtectedRouteProps: Omit<ProtectedRouteProps, "outlet"> = {
    isAuthenticated: !!sessionContext.isAuthenticated,
    authenticationPath: "/login",
  };

  return (
    <div>
      <Routes>
        <Route path="/" element={<Homepage />} />
        <Route
          path="dashboard"
          element={
            <ProtectedRoute
              {...defaultProtectedRouteProps}
              outlet={<Dashboard />}
            />
          }
        />
        <Route
          path="nested"
          element={
            <ProtectedRoute
              {...defaultProtectedRouteProps}
              outlet={<Layout />}
            />
          }
        >
          <Route path="one" element={<Protected />} />
          <Route path="two" element={<Protected />} />
        </Route>
        <Route path="login" element={<Login />} />
      </Routes>
    </div>
  );
};

to add the protected routes with the ProtectedRoute component by setting them as values for the Route component’s element prop.

Conclusion

To rewrite the protected routes using TypeScript and React-Router 6, we can define the type for the route props ourselves.

Sometimes, we want to create a TypeScript interface for objects with some known and some unknown property names.

In this article, we’ll look at how to create a TypeScript interface for objects with some known and some unknown property names.

How to create a TypeScript interface for objects with some known and some unknown property names?

To create a TypeScript interface for objects with some known and some unknown property names, we can use index signatures for the unknown properties.

For instance, we write

interface IObject {
  fixedKey1: string;
  fixedKey2: string;
  [key: string]:
    | string
    | {
        param1: number[];
        param2: string;
        param3: string;
      };
}

to add an index signature with [key: string].

This lets an object with the IObject accept any additional properties other than the ones added above.

And we set the type of the dynamic properties to string or

{
  param1: number[];
  param2: string;
  param3: string;
}

Conclusion

To create a TypeScript interface for objects with some known and some unknown property names, we can use index signatures for the unknown properties.

To fix TypeScript errors on withRouter after updating version with React Router, we can assign our own type for the route props.

For instance, we write

import { RouteComponentProps } from "react-router";

interface Props extends RouteComponentProps {
  thing: Thing | false;
  onAction?: () => void;
}

export default withRouter(({ thing, onAction, history }: Props) => {
  //...
});

to assign the { thing, onAction, history } parameter to the Props type which extends the RouteComponentProps interface provided by react-router.

This will let us add our own properties and types without the TypeScript compiler raising errors.

Sometimes, we want to fix the Typescript ‘Duplicate function implementation’ error.

In this article, we’ll look at how to fix the Typescript ‘Duplicate function implementation’ error.

How to fix the Typescript ‘Duplicate function implementation’ error?

To fix the Typescript ‘Duplicate function implementation’ error, we should make sure we didn’t define the same function multiple times.

For instance, we write

class C {
  public emit<T1>(event: string, arg1: T1): void;
  public emit<T1, T2>(event: string, arg1: T1, arg2: T2): void;
  public emit(event: string, ...args: any[]): void {
    // ...
  }
}

to add the emit method to class C with different signatures and return types to overload the method.

We only have the curly braces in the last line and we put our function implementation code in there.

Conclusion

To fix the Typescript ‘Duplicate function implementation’ error, we should make sure we didn’t define the same function multiple times.