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Eslint参考手册

规则 | Rules

no-mixed-operators

用括号括起复杂的表达式可以明确开发人员的意图,从而使代码更具可读性。此规则会在表达式中连续使用不含运算符的不同运算符时发出警告。

var foo = a && b || c || d;    /*BAD: Unexpected mix of '&&' and '||'.*/
var foo = (a && b) || c || d;  /*GOOD*/
var foo = a && (b || c || d);  /*GOOD*/

注意:对于这条规则,预计会为一对中的每个混合运算符发出一个错误。因此,对于每使用两个连续的混合运算符,都会显示一个明显的错误,指出使用违反规则的特定运算符的位置:

var foo = a && b || c || d;

会产生

1:13  Unexpected mix of '&&' and '||'. (no-mixed-operators)
1:18  Unexpected mix of '&&' and '||'. (no-mixed-operators)

规则细节

这个规则检查BinaryExpressionLogicalExpression

这个规则可能与没有额外规则的规则相冲突。如果你同时使用这个和没有额外规则的规则,你需要使用nestedBinaryExpressions no-extra-parens 规则的选项。

此规则的错误代码示例:

/*eslint no-mixed-operators: "error"*/

var foo = a && b < 0 || c > 0 || d + 1 === 0;
var foo = a + b * c;

此规则的正确代码示例:

/*eslint no-mixed-operators: "error"*/

var foo = a || b || c;
var foo = a && b && c;
var foo = (a && b < 0) || c > 0 || d + 1 === 0;
var foo = a && (b < 0 || c > 0 || d + 1 === 0);
var foo = a + (b * c);
var foo = (a + b) * c;

Options

{
    "no-mixed-operators": [
        "error",
        {
            "groups": [
                ["+", "-", "*", "/", "%", "**"],
                ["&", "|", "^", "~", "<<", ">>", ">>>"],
                ["==", "!=", "===", "!==", ">", ">=", "<", "<="],
                ["&&", "||"],
                ["in", "instanceof"]
            ],
            "allowSamePrecedence": true
        }
    ]
}

该规则有2个选项。

  • groupsstring[][]) - 指定要检查的运算符组。该groups选项是组的列表,而组是二进制运算符的列表。默认的运算符组定义为算术运算符,位运算符,比较运算符,逻辑运算符和关系运算符。
  • allowSamePrecedenceboolean) - 指定是否允许混合运算符具有相同的优先级。默认是true

groups

可以选择使用以下运算符groups

  • 算术运算符:"+""-""*""/""%""**"
  • 位运算符:"&""|""^""~""<<"">>"">>>"
  • 比较运算符:"==""!=""===""!=="">"">=""<""<="
  • 逻辑运算符:"&&""||"
  • 关系运算符:"in""instanceof"

现在,考虑下面的组配置:{"groups": [["&", "|", "^", "~", "<<", ">>", ">>>"], ["&&", "||"]]}。在此配置中指定了2组:位运算符和逻辑运算符。该规则检查操作员是否仅属于同一组。在这种情况下,该规则检查按位运算符和逻辑运算符是否混合,但忽略所有其他运算符。

此规则的代码错误代码示例{"groups": [["&", "|", "^", "~", "<<", ">>", ">>>"], ["&&", "||"]]}如下:

/*eslint no-mixed-operators: ["error", {"groups": [["&", "|", "^", "~", "<<", ">>", ">>>"], ["&&", "||"]]}]*/

var foo = a && b < 0 || c > 0 || d + 1 === 0;
var foo = a & b | c;

具有以下选项的此规则的正确代码示例{"groups": [["&", "|", "^", "~", "<<", ">>", ">>>"], ["&&", "||"]]}

/*eslint no-mixed-operators: ["error", {"groups": [["&", "|", "^", "~", "<<", ">>", ">>>"], ["&&", "||"]]}]*/

var foo = a || b > 0 || c + 1 === 0;
var foo = a && b > 0 && c + 1 === 0;
var foo = (a && b < 0) || c > 0 || d + 1 === 0;
var foo = a && (b < 0 ||  c > 0 || d + 1 === 0);
var foo = (a & b) | c;
var foo = a & (b | c);
var foo = a + b * c;
var foo = a + (b * c);
var foo = (a + b) * c;

allowSamePrecedence

具有以下选项的此规则的正确代码示例{"allowSamePrecedence": true}

/*eslint no-mixed-operators: ["error", {"allowSamePrecedence": true}]*/

// + and - have the same precedence.
var foo = a + b - c;

此规则的代码错误代码示例{"allowSamePrecedence": false}如下:

/*eslint no-mixed-operators: ["error", {"allowSamePrecedence": false}]*/

// + and - have the same precedence.
var foo = a + b - c;

何时不使用它

如果您不想收到关于混合运营商的通知,那么禁用此规则是安全的。

相关规则

  • no-extra-parensVersion 此规则是在 ESLint 2.12.0.Resources 中引入的
  • Rule source
  • Documentation source

规则 | Rules相关

1.accessor-pairs
2.array-bracket-newline
3.array-bracket-spacing
4.array-callback-return
5.array-element-newline
6.arrow-body-style
7.arrow-parens
8.arrow-spacing
9.block-scoped-var
10.block-spacing
11.brace-style
12.callback-return
13.camelcase
14.capitalized-comments
15.class-methods-use-this
16.comma-dangle
17.comma-spacing
18.comma-style
19.complexity
20.computed-property-spacing
21.consistent-return
22.consistent-this
23.constructor-super
24.curly
25.default-case
26.dot-location
27.dot-notation
28.eol-last
29.eqeqeq
30.for-direction
31.func-call-spacing
32.func-name-matching
33.func-names
34.func-style
35.function-paren-newline
36.generator-star
37.generator-star-spacing
38.getter-return
39.global-require
40.global-strict
41.guard-for-in
42.handle-callback-err
43.id-blacklist
44.id-length
45.id-match
46.implicit-arrow-linebreak
47.indent
48.indent-legacy
49.init-declarations
50.jsx-quotes
51.key-spacing
52.keyword-spacing
53.line-comment-position
54.linebreak-style
55.lines-around-comment
56.lines-around-directive
57.lines-between-class-members
58.max-depth
59.max-len
60.max-lines
61.max-nested-callbacks
62.max-params
63.max-statements
64.max-statements-per-line
65.multiline-comment-style
66.multiline-ternary
67.new-cap
68.new-parens
69.newline-after-var
70.newline-before-return
71.newline-per-chained-call
72.no-alert
73.no-array-constructor
74.no-arrow-condition
75.no-await-in-loop
76.no-bitwise
77.no-buffer-constructor
78.no-caller
79.no-case-declarations
80.no-catch-shadow
81.no-class-assign
82.no-comma-dangle
83.no-compare-neg-zero
84.no-cond-assign
85.no-confusing-arrow
86.no-console
87.no-const-assign
88.no-constant-condition
89.no-continue
90.no-control-regex
91.no-debugger
92.no-delete-var
93.no-div-regex
94.no-dupe-args
95.no-dupe-class-members
96.no-dupe-keys
97.no-duplicate-case
98.no-duplicate-imports
99.no-else-return
100.no-empty
Eslint

ESLint 是一个代码规范和错误检查工具,有以下几个特性。所有东西都是可以插拔的。你可以调用任意的 rule api 或者 formatter api 去打包或者定义 rule or formatter。任意的 rule 都是独立的。没有特定的 coding style,你可以自己配置。

主页 https://eslint.org/
源码 https://github.com/eslint/eslint
发布版本 4.12.0

Eslint目录

1.指南 | Guide
2.规则 | Rules