Prevent missing key props in iterators/collection literals

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

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Metadata

ID: jsx-react/jsx-key

Language: JavaScript

Severity: Error

Category: Error Prone

Description

In JSX you need to specify a key prop for each item of a list because if it’s missing it could 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 }} />