problem
this.props.key in the component will get undefined .
the reason
Most of the props on JSX elements will be passed to the component, but there are two special props ( ref and key ) that have been used by React and will not be passed to the component.
solution
<ListItem key={result.id} id={result.id} /> with a different prop. Although this may seem redundant, it is important to separate application logic from reconciliation hints.
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