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max-len.md

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规则名 规则类型 关联规则
max-len
layout
complexity
max-depth
max-nested-callbacks
max-params
max-statements

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).

var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" }; // very long

规则详解

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.

配置项

This rule has a number or object option:

  • "code" (default 80) enforces a maximum line length
  • "tabWidth" (default 4) specifies the character width for tab characters
  • "comments" enforces a maximum line length for comments; defaults to value of code
  • "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
  • "ignoreComments": true ignores all trailing comments and comments on their own line
  • "ignoreTrailingComments": true ignores only trailing comments
  • "ignoreUrls": true ignores lines that contain a URL
  • "ignoreStrings": true ignores lines that contain a double-quoted or single-quoted string
  • "ignoreTemplateLiterals": true ignores lines that contain a template literal
  • "ignoreRegExpLiterals": true ignores lines that contain a RegExp literal

code

选项 { "code": 80 } 默认值的 错误 代码示例：

/*eslint max-len: ["error", { "code": 80 }]*/

var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" };

选项 { "code": 80 } 默认值的 正确 代码示例：

::: correct

/*eslint max-len: ["error", { "code": 80 }]*/

var foo = {
  "bar": "This is a bar.",
  "baz": { "qux": "This is a qux" },
  "easier": "to read"
};

tabWidth

选项 { "tabWidth": 4 } 默认值的 错误 代码示例：

/*eslint max-len: ["error", { "code": 80, "tabWidth": 4 }]*/

\t  \t  var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" } };

选项 { "tabWidth": 4 } 默认值的 正确 代码示例：

::: correct

/*eslint max-len: ["error", { "code": 80, "tabWidth": 4 }]*/

\t  \t  var foo = {
\t  \t  \t  \t  "bar": "This is a bar.",
\t  \t  \t  \t  "baz": { "qux": "This is a qux" }
\t  \t  };

comments

选项 { "comments": 65 } 的 错误 代码示例：

/*eslint max-len: ["error", { "comments": 65 }]*/

/**
 * This is a comment that violates the maximum line length we have specified
**/

ignoreComments

选项 { "ignoreComments": true } 的 正确 代码示例：

::: correct

/*eslint max-len: ["error", { "ignoreComments": true }]*/

/**
 * This is a really really really really really really really really really long comment
**/

ignoreTrailingComments

选项 { "ignoreTrailingComments": true } 的 正确 代码示例：

::: correct

/*eslint max-len: ["error", { "ignoreTrailingComments": true }]*/

var foo = 'bar'; // This is a really really really really really really really long comment

ignoreUrls

选项 { "ignoreUrls": true } 的 正确 代码示例：

::: correct

/*eslint max-len: ["error", { "ignoreUrls": true }]*/

var url = 'https://www.example.com/really/really/really/really/really/really/really/long';

ignoreStrings

选项 { "ignoreStrings": true } 的 正确 代码示例：

::: correct

/*eslint max-len: ["error", { "ignoreStrings": true }]*/

var longString = 'this is a really really really really really long string!';

ignoreTemplateLiterals

选项 { "ignoreTemplateLiterals": true } 的 正确 代码示例：

::: correct

/*eslint max-len: ["error", { "ignoreTemplateLiterals": true }]*/

var longTemplateLiteral = `this is a really really really really really long template literal!`;

ignoreRegExpLiterals

选项 { "ignoreRegExpLiterals": true } 的 正确 代码示例：

::: correct

/*eslint max-len: ["error", { "ignoreRegExpLiterals": true }]*/

var longRegExpLiteral = /this is a really really really really really long regular expression!/;

ignorePattern

选项 ignorePattern 的 正确 代码示例：

::: correct

/*eslint max-len: ["error", { "ignorePattern": "^\\s*var\\s.+=\\s*require\\s*\\(" }]*/

var dep = require('really/really/really/really/really/really/really/really/long/module');