How to Resolve “Type is not assignable” Error in TypeScript for React Components

Problem:

When using TypeScript in a React project, you may encounter an error like:

Type ‘{ employeeId: any; weekRange: { start: Date; end: Date; }; }’ is not assignable to type ‘IntrinsicAttributes & { projectTask: string; }’.

 Property ’employeeId’ does not exist on type ‘IntrinsicAttributes & { projectTask: string; }’.ts(2322)

This typically happens when the props passed to a component do not match the props expected by that component.

Solution:

1. Identify the Issue:
2. Determine which component is causing the error and what props it expects. In this example, the WeeklyTimeEntries component is expecting a prop named projectTask, but employeeId and weekRange are being passed instead.
3. Update Component Props:
4. Modify the WeeklyTimeEntries component to accept the correct props.

Step-by-Step Solution:

1. Define the Props Interface:

Create an interface for the props expected by the component.

import React, { useEffect, useState } from ‘react’;

interface WeeklyTimeEntriesProps {

 employeeId: string;

 weekRange: { start: Date; end: Date };

}

2.Update the Component Definition:

Adjust the component to use the new props interface.

const WeeklyTimeEntries: React.FC<WeeklyTimeEntriesProps> = ({ employeeId, weekRange }) => {

 const [timeEntries, setTimeEntries] = useState([]);

 useEffect(() => {

  const fetchTimeEntries = async () => {

   try {

    const response = await fetch(`http://localhost:8000/api/timeEntries?employeeId=${employeeId}&start=${weekRange.start.toISOString()}&end=${weekRange.end.toISOString()}`);

    const data = await response.json();

    setTimeEntries(data);

   } catch (error) {

    console.error(‘Error fetching time entries:’, error);

   }

  };

  fetchTimeEntries();

 }, [employeeId, weekRange]);

 return (

  <div>

   <h2 className=”text-lg font-semibold”>Weekly Time Entries</h2>

   <ul>

    {timeEntries.map((entry) => (

     <li key={entry.id}>{entry.description} – {entry.hours} hours</li>

    ))}

   </ul>

  </div>

 );

};

export default WeeklyTimeEntries;

3.Pass Correct Props:

Ensure the parent component passes the correct props to WeeklyTimeEntries.

<td className=”p-3 px-5″>

 <WeeklyTimeEntries employeeId={user.internalid} weekRange={weekRange} />

</td>

By following these steps, you can resolve the “Type is not assignable” error, ensuring that your components receive the correct props and TypeScript validation is satisfied.

When you encounter a type mismatch error in TypeScript for React components, identify the expected props and update both the component definition and the parent component to match. Use TypeScript interfaces to define and enforce the prop types, ensuring your components communicate effectively.