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66 lines
1.5 KiB
Text
66 lines
1.5 KiB
Text
---
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description: 'Enforce using `String#startsWith` and `String#endsWith` over other equivalent methods of checking substrings.'
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---
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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/prefer-string-starts-ends-with** for documentation.
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There are multiple ways to verify if a string starts or ends with a specific string, such as `foo.indexOf('bar') === 0`.
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Since ES2015 has added `String#startsWith` and `String#endsWith`, this rule reports other ways to be consistent.
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## Rule Details
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This rule is aimed at enforcing a consistent way to check whether a string starts or ends with a specific string.
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Examples of code for this rule:
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<!--tabs-->
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### ❌ Incorrect
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```ts
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let foo: string;
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// starts with
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foo[0] === 'b';
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foo.charAt(0) === 'b';
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foo.indexOf('bar') === 0;
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foo.slice(0, 3) === 'bar';
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foo.substring(0, 3) === 'bar';
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foo.match(/^bar/) != null;
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/^bar/.test(foo);
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// ends with
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foo[foo.length - 1] === 'b';
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foo.charAt(foo.length - 1) === 'b';
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foo.lastIndexOf('bar') === foo.length - 3;
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foo.slice(-3) === 'bar';
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foo.substring(foo.length - 3) === 'bar';
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foo.match(/bar$/) != null;
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/bar$/.test(foo);
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```
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### ✅ Correct
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```ts
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foo.startsWith('bar');
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foo.endsWith('bar');
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```
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## Options
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```jsonc
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// .eslintrc.json
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{
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"rules": {
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"@typescript-eslint/prefer-string-starts-ends-with": "warn"
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}
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}
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```
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This rule is not configurable.
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## When Not To Use It
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If you don't mind that style, you can turn this rule off safely.
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