no-underscore-dangle

禁止标识符中的悬空下划线

就标识符的命名约定而言，悬空下划线可能是 JavaScript 中最极端的。悬空下划线是标识符开头或结尾的下划线，例如：

var _foo;

实际上，在 JavaScript 中使用悬空下划线来指示对象的 "private" 成员实际上由来已久（尽管 JavaScript 没有真正的私有成员，但这种约定是一种警告）。这始于 SpiderMonkey 添加非标准方法，例如 __defineGetter__()。带有下划线的目的是为了表明这种方法在某些方面是特殊的。从那时起，使用单个下划线前缀作为一种表示对象的 "private" 成员的方式变得流行起来。

您是否选择允许在标识符中使用悬空下划线纯粹是一种约定，对性能、可读性或复杂性没有影响。这纯粹是一种偏好。

规则详情

此规则不允许在标识符中使用悬空下划线。

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/*eslint no-underscore-dangle: "error"*/

var foo_;
var __proto__ = {};
foo._bar();

FphvHt5MK/G5o4JKMpo8wFZScNX7kGyQzE3xqEeYlFcVQkbgr+qufrIGgDR/9BRp

/*eslint no-underscore-dangle: "error"*/

var _ = require('underscore');
var obj = _.contains(items, item);
obj.__proto__ = {};
var file = __filename;
function foo(_bar) {};
const foo = { onClick(_bar) {} };
const foo = (_bar) => {};

选项

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allow

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/*eslint no-underscore-dangle: ["error", { "allow": ["foo_", "_bar"] }]*/

var foo_;
foo._bar();

allowAfterThis

nQP82WYZJTVvhOZX4UTE6KFRAS7rRlCuQCMvsdIyG6d1bBau1MZBSWrI8Yx1GnGNDLCnSKezzNSqyZRDsHfNld0juzqd8UqdPfD64Ghs6h5i5AIfuLWNc609O4PW6bgj

/*eslint no-underscore-dangle: ["error", { "allowAfterThis": true }]*/

var a = this.foo_;
this._bar();

allowAfterSuper

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/*eslint no-underscore-dangle: ["error", { "allowAfterSuper": true }]*/

var a = super.foo_;
super._bar();

allowAfterThisConstructor

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/*eslint no-underscore-dangle: ["error", { "allowAfterThisConstructor": true }]*/

var a = this.constructor.foo_;
this.constructor._bar();

enforceInMethodNames

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/*eslint no-underscore-dangle: ["error", { "enforceInMethodNames": true }]*/

class Foo {
  _bar() {}
}

class Foo {
  bar_() {}
}

const o = {
  _bar() {}
};

const o = {
  bar_() = {}
};

enforceInClassFields

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/*eslint no-underscore-dangle: ["error", { "enforceInClassFields": true }]*/

class Foo {
    _bar;
}

class Foo {
    _bar = () => {};
}

class Foo {
    bar_;
}

class Foo {
    #_bar;
}

class Foo {
    #bar_;
}

allowInArrayDestructuring

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/*eslint no-underscore-dangle: ["error", { "allowInArrayDestructuring": false }]*/

const [_foo, _bar] = list;
const [foo_, ..._bar] = list;
const [foo, [bar, _baz]] = list;

allowInObjectDestructuring

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/*eslint no-underscore-dangle: ["error", { "allowInObjectDestructuring": false }]*/

const { foo, bar: _bar } = collection;
const { foo, bar, _baz } = collection;

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/*eslint no-underscore-dangle: ["error", { "allowInObjectDestructuring": false }]*/

const { foo, bar, _baz: { a, b } } = collection;
const { foo, bar, _baz: baz } = collection;

allowFunctionParams

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/*eslint no-underscore-dangle: ["error", { "allowFunctionParams": false }]*/

function foo (_bar) {}
function foo (_bar = 0) {}
function foo (..._bar) {}

const foo = function onClick (_bar) {}
const foo = function onClick (_bar = 0) {}
const foo = function onClick (..._bar) {}

const foo = (_bar) => {};
const foo = (_bar = 0) => {};
const foo = (..._bar) => {};

何时不使用

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