61 lines
1.1 KiB
Plaintext
61 lines
1.1 KiB
Plaintext
---
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description: 'Disallow extra non-null assertions.'
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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-extra-non-null-assertion** for documentation.
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The `!` non-null assertion operator in TypeScript is used to assert that a value's type does not include `null` or `undefined`.
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Using the operator any more than once on a single value does nothing.
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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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const foo: { bar: number } | null = null;
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const bar = foo!!!.bar;
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```
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```ts
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function foo(bar: number | undefined) {
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const bar: number = bar!!!;
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}
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```
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```ts
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function foo(bar?: { n: number }) {
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return bar!?.n;
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}
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```
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</TabItem>
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<TabItem value="✅ Correct">
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```ts
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const foo: { bar: number } | null = null;
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const bar = foo!.bar;
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```
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```ts
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function foo(bar: number | undefined) {
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const bar: number = bar!;
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}
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```
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```ts
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function foo(bar?: { n: number }) {
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return bar?.n;
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}
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```
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</TabItem>
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</Tabs>
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{/* Intentionally Omitted: When Not To Use It */}
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