func-style

强制一致地使用 function 声明或表达式

在 JavaScript 中有两种定义函数的方式：function 声明和 function 表达式。声明首先包含 function 关键字，然后是名称，然后是其参数和函数体，例如：

function doSomething() {
    // ...
}

等效函数表达式以 var 关键字开头，后跟名称，然后是函数本身，例如：

var doSomething = function() {
    // ...
};

function 声明和 function expressions 之间的主要区别在于声明被提升到定义它们的范围的顶部，这允许您编写在声明之前使用函数的代码。例如：

doSomething();

function doSomething() {
    // ...
}

尽管这段代码看起来像是一个错误，但实际上它运行良好，因为 JavaScript 引擎将 function 声明提升到了作用域的顶部。这意味着此代码被视为声明出现在调用之前。

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doSomething();  // error!

var doSomething = function() {
    // ...
};

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规则详情

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选项

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expression

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/*eslint func-style: ["error", "expression"]*/

function foo() {
    // ...
}

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/*eslint func-style: ["error", "expression"]*/

var foo = function() {
    // ...
};

var foo = () => {};

// allowed as allowArrowFunctions : false is applied only for declaration

declaration

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/*eslint func-style: ["error", "declaration"]*/

var foo = function() {
    // ...
};

var foo = () => {};

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/*eslint func-style: ["error", "declaration"]*/

function foo() {
    // ...
}

// Methods (functions assigned to objects) are not checked by this rule
SomeObject.foo = function() {
    // ...
};

allowArrowFunctions

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/*eslint func-style: ["error", "declaration", { "allowArrowFunctions": true }]*/

var foo = () => {};

何时不使用

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