https://stackoverflow.com/questions/48266018/missing-key-prop-for-element-reactjs-and-typescript
When rendering an array of elements, React needs a key
prop (1) to identify elements and optimize things.
Add key={topic.id}
to your element in jsx:
return ( <div> <h2>Results List</h2> {topics.map((topic: any) => <div className="panel panel-default" key={topic.id}> <div className="panel-heading">{topic.name}</div> <div className="panel-body">{topic.description}</div> </div> )} </div> );