no-multi-assign

禁止使用链式赋值表达式

链式变量赋值可能导致意外结果，并且难以阅读。

(function() {
    const foo = bar = 0; // Did you mean `foo = bar == 0`?
    bar = 1;             // This will not fail since `bar` is not constant.
})();
console.log(bar);        // This will output 1 since `bar` is not scoped.
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规则详情

此规则禁止在单个语句中使用多个赋值。

此规则的 错误 代码示例

/*eslint no-multi-assign: "error"*/

let a = b = c = 5;

const foo = bar = "baz";

let d =
    e =
    f;

class Foo {
    a = b = 10;
}

a = b = "quux";
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此规则的 正确 代码示例

/*eslint no-multi-assign: "error"*/

let a = 5;
let b = 5;
const c = 5;

const foo = "baz";
const bar = "baz";

let d = c;
let e = c;

class Foo {
    a = 10;
    b = 10;
}

a = "quux";
b = "quux";
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选项

此规则有一个对象选项

• `ignoreNonDeclaration`：当设置为 `true` 时，此规则允许不包含在声明中初始化变量或初始化类字段的链。 默认为 `false`。

ignoreNonDeclaration

`{ "ignoreNonDeclaration": true }` 选项的 正确 代码示例

/*eslint no-multi-assign: ["error", { "ignoreNonDeclaration": true }]*/

let a;
let b;
a = b = "baz";

const x = {};
const y = {};
x.one = y.one = 1;
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`{ "ignoreNonDeclaration": true }` 选项的 错误 代码示例

/*eslint no-multi-assign: ["error", { "ignoreNonDeclaration": true }]*/

let a = b = "baz";

const foo = bar = 1;

class Foo {
    a = b = 10;
}
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相关规则

• max-statements-per-line

版本

此规则在 ESLint v3.14.0 中引入。

资源

• 规则源码
• 测试源码