no-duplicate-key

Full Name in eslint-plugin-react-x

react-x/no-duplicate-key

Full Name in @eslint-react/eslint-plugin

@eslint-react/no-duplicate-key

Presets

x
recommended
recommended-typescript
recommended-type-checked

Description

Disallow duplicate key on elements in the same array or a list of children.

React uses keys to identify elements in an array. If two elements have the same key, React will not be able to distinguish them. This can lead to issues with state and rendering.

Examples

Failing

import React from 'react';

function MyComponent () {
  return [
    <li key="1">Item 1</li>
    <li key="1">Item 2</li>
    //  ^^^^^^^
    //  - A key must be unique. 'key="1"' is duplicated.
  ]
};

import React from "react";

function MyComponent() {
  return (
    <ul>
      <li key="1">Item 1</li>
      <li key="1">Item 2</li>
      {/* ^^^^^^^ */}
      {/* - A key must be unique. 'key="1"' is duplicated. */}
    </ul>
  );
}

import React from "react";

function MyComponent() {
  return (
    <ul>
      {["a", "b"].map((id) => <li key="1">{id}</li>)}
    </ul>
  );
  //                                     ^^^^^^^
  //                                     - A key must be unique. 'key="1"' is duplicated.
}

Passing

import React from 'react';

function MyComponent () {
  return [
    <li key="1">Item 1</li>
    <li key="2">Item 2</li>
  ]
};

import React from "react";

function MyComponent() {
  return (
    <ul>
      <li key="1">Item 1</li>
      <li key="2">Item 2</li>
    </ul>
  );
}

import React from "react";

function MyComponent() {
  return (
    <ul>
      {["a", "b"].map((id) => <li key={id}>{id}</li>)}
    </ul>
  );
}

Description

Examples

Failing

Passing

Implementation

Further Reading

See Also

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