97 lines
1.9 KiB
Plaintext
97 lines
1.9 KiB
Plaintext
---
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description: 'Disallow enums from having both number and string members.'
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---
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import Tabs from '@theme/Tabs';
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import TabItem from '@theme/TabItem';
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> 🛑 This file is source code, not the primary documentation location! 🛑
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>
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> See **https://typescript-eslint.io/rules/no-mixed-enums** for documentation.
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TypeScript enums are allowed to assign numeric or string values to their members.
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Most enums contain either all numbers or all strings, but in theory you can mix-and-match within the same enum.
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Mixing enum member types is generally considered confusing and a bad practice.
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## Examples
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<Tabs>
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<TabItem value="❌ Incorrect">
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```ts
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enum Status {
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Unknown,
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Closed = 1,
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Open = 'open',
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}
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```
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</TabItem>
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<TabItem value="✅ Correct (Explicit Numbers)">
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```ts
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enum Status {
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Unknown = 0,
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Closed = 1,
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Open = 2,
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}
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```
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</TabItem>
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<TabItem value="✅ Correct (Implicit Numbers)">
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```ts
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enum Status {
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Unknown,
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Closed,
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Open,
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}
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```
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</TabItem>
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<TabItem value="✅ Correct (Strings)">
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```ts
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enum Status {
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Unknown = 'unknown',
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Closed = 'closed',
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Open = 'open',
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}
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```
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</TabItem>
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</Tabs>
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## Iteration Pitfalls of Mixed Enum Member Values
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Enum values may be iterated over using `Object.entries`/`Object.keys`/`Object.values`.
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If all enum members are strings, the number of items will match the number of enum members:
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```ts
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enum Status {
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Closed = 'closed',
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Open = 'open',
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}
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// ['closed', 'open']
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Object.values(Status);
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```
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But if the enum contains members that are initialized with numbers -including implicitly initialized numbers— then iteration over that enum will include those numbers as well:
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```ts
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enum Status {
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Unknown,
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Closed = 1,
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Open = 'open',
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}
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// ["Unknown", "Closed", 0, 1, "open"]
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Object.values(Status);
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```
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## When Not To Use It
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If you don't mind the confusion of mixed enum member values and don't iterate over enums, you can safely disable this rule.
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