Prevent missing key props in iterators/collection literals

Docs > Code Analysis > Static Analysis Rules > Prevent missing key props in iterators/collection literals

This page is not yet available in Spanish. We are working on its translation.
If you have any questions or feedback about our current translation project, feel free to reach out to us!

Metadata

ID: tsx-react/tsx-key

Language: TypeScript

Severity: Error

Category: Error Prone

Description

In JSX you need to specify a key prop for each item of a list. A missing key prop can lead to unexpected renders or stale UI. This rule checks for possible JSX lists and warns if the key prop is missing.

Non-Compliant Code Examples

[<></>];
[<Hello a="foo" />, <Hello>foo</Hello>, <Hello />];
[<Hello />, <Hello a="">foo</Hello>, <Hello />];
data.map(x => <Hello a="" />);
data.map(x => <Hello>{x}</Hello>);
data.map(x => <Hello a="">{x}</Hello>);
data.map(x => { return <Hello>{x}</Hello>});
data.map(x => { return <Hello a="">{x}</Hello>});
data.map(function(x) { return <Hello>{x}</Hello>});
data.map(function(x) { return <Hello>{x}</Hello>});
Array.from([1, 2, 3], (x) => <Hello>{x}</Hello>);

Compliant Code Examples

[<Hello key="first" test="foo" />, <Hello key="second" />, <Hello key="third" />];
data.map((x) => <Hello key={x.id}>{x}</Hello>);
Array.from([1, 2, 3], (x) => <Hello key={x.id}>{x}</Hello>);
<Hello key={id} {...{ id, caption }} />