logical-assignment-operators

要求或禁止逻辑赋值运算符速记

ES2021 引入了逻辑运算符 ||、&& 和 ?? 的赋值运算符简写。以前，这仅允许用于数学运算，例如 + 或 *（参见规则 operator-assignment）。如果赋值目标和逻辑表达式的左表达式相同，则可以使用简写。例如 a = a || b 可以缩短为 a ||= b。

¥ES2021 introduces the assignment operator shorthand for the logical operators ||, && and ??. Before, this was only allowed for mathematical operations such as + or * (see the rule operator-assignment). The shorthand can be used if the assignment target and the left expression of a logical expression are the same. For example a = a || b can be shortened to a ||= b.

规则详情

¥Rule Details

此规则要求或禁止逻辑赋值运算符简写。

¥This rule requires or disallows logical assignment operator shorthand.

选项

¥Options

该规则有一个字符串和一个对象选项。字符串选项：

¥This rule has a string and an object option. String option:

• "always"（默认）

  ¥"always" (default)

• "never"

对象选项（仅当字符串选项设置为 "always" 时可用）：

¥Object option (only available if string option is set to "always"):

• "enforceForIfStatements": false（默认）不检查等效的 if 语句

  ¥"enforceForIfStatements": false(default) Do not check for equivalent if statements

• "enforceForIfStatements": true 检查等效的 if 语句

  ¥"enforceForIfStatements": true Check for equivalent if statements

always

此选项检查可以使用逻辑赋值运算符缩短的表达式。例如，a = a || b 可以缩短为 a ||= b。据报告，具有结合性的表达式（例如 a = a || b || c）可以缩短为 a ||= b || c，除非使用括号明确定义计算顺序（例如 a = (a || b) || c）。

¥This option checks for expressions that can be shortened using logical assignment operator. For example, a = a || b can be shortened to a ||= b. Expressions with associativity such as a = a || b || c are reported as being able to be shortened to a ||= b || c unless the evaluation order is explicitly defined using parentheses, such as a = (a || b) || c.

使用默认 "always" 选项的此规则的错误代码示例：

¥Examples of incorrect code for this rule with the default "always" option:

/*eslint logical-assignment-operators: ["error", "always"]*/

a = a || b
a = a && b
a = a ?? b
a || (a = b)
a && (a = b)
a ?? (a = b)
a = a || b || c
a = a && b && c
a = a ?? b ?? c
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使用默认 "always" 选项的此规则的正确代码示例：

¥Examples of correct code for this rule with the default "always" option:

/*eslint logical-assignment-operators: ["error", "always"]*/

a = b
a += b
a ||= b
a = b || c
a || (b = c)

if (a) a = b

a = (a || b) || c
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never

使用 "never" 选项的此规则的错误代码示例：

¥Examples of incorrect code for this rule with the "never" option:

/*eslint logical-assignment-operators: ["error", "never"]*/

a ||= b
a &&= b
a ??= b
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使用 "never" 选项的此规则的正确代码示例：

¥Examples of correct code for this rule with the "never" option:

/*eslint logical-assignment-operators: ["error", "never"]*/

a = a || b
a = a && b
a = a ?? b
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enforceForIfStatements

此选项使用可以用逻辑赋值运算符表示的 if 语句检查其他模式。

¥This option checks for additional patterns with if statements which could be expressed with the logical assignment operator.

使用 ["always", { enforceForIfStatements: true }] 选项的此规则的错误代码示例：

¥Examples of incorrect code for this rule with the ["always", { enforceForIfStatements: true }] option:

/*eslint logical-assignment-operators: ["error", "always", { enforceForIfStatements: true }]*/

if (a) a = b // <=> a &&= b
if (!a) a = b // <=> a ||= b

if (a == null) a = b // <=> a ??= b
if (a === null || a === undefined) a = b // <=> a ??= b
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使用 ["always", { enforceForIfStatements: true }] 选项的此规则的正确代码示例：

¥Examples of correct code for this rule with the ["always", { enforceForIfStatements: true }] option:

/*eslint logical-assignment-operators: ["error", "always", { enforceForIfStatements: true }]*/

if (a) b = c
if (a === 0) a = b
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何时不使用

¥When Not To Use It

使用逻辑运算符赋值速记是一种风格选择。关闭此规则将允许开发者根据具体情况选择哪种样式更具可读性。

¥Use of logical operator assignment shorthand is a stylistic choice. Leaving this rule turned off would allow developers to choose which style is more readable on a case-by-case basis.

版本

此规则是在 ESLint v8.24.0 中引入。

资源

• 规则源码
• 测试源码