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eb39fafa4f
includes a (minimal) working wrapper Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
162 lines
4.8 KiB
Markdown
162 lines
4.8 KiB
Markdown
# enforce a maximum line length (max-len)
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Very long lines of code in any language can be difficult to read. In order to aid in readability and maintainability many coders have developed a convention to limit lines of code to X number of characters (traditionally 80 characters).
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```js
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var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" }; // very long
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```
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## Rule Details
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This rule enforces a maximum line length to increase code readability and maintainability. The length of a line is defined as the number of Unicode characters in the line.
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## Options
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This rule has a number or object option:
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* `"code"` (default `80`) enforces a maximum line length
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* `"tabWidth"` (default `4`) specifies the character width for tab characters
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* `"comments"` enforces a maximum line length for comments; defaults to value of `code`
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* `"ignorePattern"` ignores lines matching a regular expression; can only match a single line and need to be double escaped when written in YAML or JSON
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* `"ignoreComments": true` ignores all trailing comments and comments on their own line
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* `"ignoreTrailingComments": true` ignores only trailing comments
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* `"ignoreUrls": true` ignores lines that contain a URL
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* `"ignoreStrings": true` ignores lines that contain a double-quoted or single-quoted string
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* `"ignoreTemplateLiterals": true` ignores lines that contain a template literal
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* `"ignoreRegExpLiterals": true` ignores lines that contain a RegExp literal
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### code
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Examples of **incorrect** code for this rule with the default `{ "code": 80 }` option:
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```js
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/*eslint max-len: ["error", { "code": 80 }]*/
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var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" };
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```
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Examples of **correct** code for this rule with the default `{ "code": 80 }` option:
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```js
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/*eslint max-len: ["error", { "code": 80 }]*/
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var foo = {
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"bar": "This is a bar.",
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"baz": { "qux": "This is a qux" },
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"easier": "to read"
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};
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```
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### tabWidth
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Examples of **incorrect** code for this rule with the default `{ "tabWidth": 4 }` option:
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```js
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/*eslint max-len: ["error", { "code": 80, "tabWidth": 4 }]*/
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\t \t var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" } };
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```
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Examples of **correct** code for this rule with the default `{ "tabWidth": 4 }` option:
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```js
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/*eslint max-len: ["error", { "code": 80, "tabWidth": 4 }]*/
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\t \t var foo = {
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\t \t \t \t "bar": "This is a bar.",
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\t \t \t \t "baz": { "qux": "This is a qux" }
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\t \t };
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```
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### comments
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Examples of **incorrect** code for this rule with the `{ "comments": 65 }` option:
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```js
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/*eslint max-len: ["error", { "comments": 65 }]*/
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/**
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* This is a comment that violates the maximum line length we have specified
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**/
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```
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### ignoreComments
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Examples of **correct** code for this rule with the `{ "ignoreComments": true }` option:
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```js
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/*eslint max-len: ["error", { "ignoreComments": true }]*/
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/**
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* This is a really really really really really really really really really long comment
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**/
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```
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### ignoreTrailingComments
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Examples of **correct** code for this rule with the `{ "ignoreTrailingComments": true }` option:
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```js
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/*eslint max-len: ["error", { "ignoreTrailingComments": true }]*/
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var foo = 'bar'; // This is a really really really really really really really long comment
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```
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### ignoreUrls
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Examples of **correct** code for this rule with the `{ "ignoreUrls": true }` option:
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```js
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/*eslint max-len: ["error", { "ignoreUrls": true }]*/
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var url = 'https://www.example.com/really/really/really/really/really/really/really/long';
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```
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### ignoreStrings
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Examples of **correct** code for this rule with the `{ "ignoreStrings": true }` option:
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```js
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/*eslint max-len: ["error", { "ignoreStrings": true }]*/
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var longString = 'this is a really really really really really long string!';
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```
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### ignoreTemplateLiterals
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Examples of **correct** code for this rule with the `{ "ignoreTemplateLiterals": true }` option:
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```js
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/*eslint max-len: ["error", { "ignoreTemplateLiterals": true }]*/
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var longTemplateLiteral = `this is a really really really really really long template literal!`;
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```
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### ignoreRegExpLiterals
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Examples of **correct** code for this rule with the `{ "ignoreRegExpLiterals": true }` option:
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```js
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/*eslint max-len: ["error", { "ignoreRegExpLiterals": true }]*/
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var longRegExpLiteral = /this is a really really really really really long regular expression!/;
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```
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### ignorePattern
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Examples of **correct** code for this rule with the `ignorePattern` option:
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```js
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/*eslint max-len: ["error", { "ignorePattern": "^\\s*var\\s.+=\\s*require\\s*\\(" }]*/
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var dep = require('really/really/really/really/really/really/really/really/long/module');
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```
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## Related Rules
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* [complexity](complexity.md)
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* [max-depth](max-depth.md)
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* [max-nested-callbacks](max-nested-callbacks.md)
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* [max-params](max-params.md)
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* [max-statements](max-statements.md)
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