max-len

强制执行最大行长度

任何语言中过长的代码行都可能难以阅读。为了帮助提高可读性和可维护性，许多程序员制定了一个约定，将代码行限制为 X 个字符（传统上为 80 个字符）。

var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" }; // very long
1

规则详情

此规则强制执行最大行长度，以提高代码的可读性和可维护性。行的长度定义为行中 Unicode 字符的数量。

选项

此规则最多可以有两个数字作为位置参数（用于 code 和 tabWidth 选项），后跟一个对象选项（前提是位置参数具有优先级）

• "code"（默认值 80）强制执行最大行长度
• "tabWidth"（默认值 4）指定制表符的字符宽度
• "comments" 强制执行注释的最大行长度；默认为 code 的值
• "ignorePattern" 忽略与正则表达式匹配的行；只能匹配单行，并且在 YAML 或 JSON 中编写时需要双重转义
• "ignoreComments": true 忽略所有尾随注释和独占一行的注释
• "ignoreTrailingComments": true 仅忽略尾随注释
• "ignoreUrls": true 忽略包含 URL 的行
• "ignoreStrings": true 忽略包含双引号或单引号字符串的行
• "ignoreTemplateLiterals": true 忽略包含模板字面量的行
• "ignoreRegExpLiterals": true 忽略包含 RegExp 字面量的行

code

此规则在默认 { "code": 80 } 选项下错误代码示例

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

var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" };
1
2
3

此规则在默认 { "code": 80 } 选项下正确代码示例

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

var foo = {
  "bar": "This is a bar.",
  "baz": { "qux": "This is a qux" },
  "easier": "to read"
};
1
2
3
4
5
6
7

tabWidth

此规则在默认 { "tabWidth": 4 } 选项下错误代码示例

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

		var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" } };
1
2
3

此规则在默认 { "tabWidth": 4 } 选项下正确代码示例

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

		var foo = {
				"bar": "This is a bar.",
				"baz": { "qux": "This is a qux" }
		};
1
2
3
4
5
6

comments

此规则在 { "comments": 65 } 选项下错误代码示例

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

/**
 * This is a comment that violates the maximum line length we have specified
**/
1
2
3
4
5

ignoreComments

此规则在 { "ignoreComments": true } 选项下正确代码示例

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

/**
 * This is a really really really really really really really really really long comment
**/
1
2
3
4
5

ignoreTrailingComments

此规则在 { "ignoreTrailingComments": true } 选项下正确代码示例

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

var foo = 'bar'; // This is a really really really really really really really long comment
1
2
3

ignoreUrls

此规则在 { "ignoreUrls": true } 选项下正确代码示例

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

var url = 'https://www.example.com/really/really/really/really/really/really/really/long';
1
2
3

ignoreStrings

此规则在 { "ignoreStrings": true } 选项下正确代码示例

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

var longString = 'this is a really really really really really long string!';
1
2
3

ignoreTemplateLiterals

此规则在 { "ignoreTemplateLiterals": true } 选项下正确代码示例

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

var longTemplateLiteral = `this is a really really really really really long template literal!`;
1
2
3

ignoreRegExpLiterals

此规则在 { "ignoreRegExpLiterals": true } 选项下正确代码示例

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

var longRegExpLiteral = /this is a really really really really really long regular expression!/;
1
2
3

ignorePattern

此规则在 ignorePattern 选项下正确代码示例

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

var dep = require('really/really/really/really/really/really/really/really/long/module');
1
2
3
4

相关规则

• complexity
• max-depth
• max-nested-callbacks
• max-params
• max-statements

版本

此规则在 ESLint v0.0.9 中引入。

资源

• 规则源
• 测试源