no-shadow

禁止在外部作用域中声明的隐藏变量中的变量声明

影子化是局部变量与其包含范围内的变量共享相同名称的过程。例如：

var a = 3;
function b() {
    var a = 10;
}

在这种情况下，b() 内部的变量 a 将在全局范围内隐藏变量 a。这可能会在阅读代码时造成混乱，并且无法访问全局变量。

规则详情

该规则旨在消除阴影变量声明。

此规则的错误代码示例：

/*eslint no-shadow: "error"*/
/*eslint-env es6*/

var a = 3;
function b() {
    var a = 10;
}

var b = function () {
    var a = 10;
}

function b(a) {
    a = 10;
}
b(a);

if (true) {
    let a = 5;
}

选项

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{
    "no-shadow": ["error", { "builtinGlobals": false, "hoist": "functions", "allow": [], "ignoreOnInitialization": false }]
}

builtinGlobals

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/*eslint no-shadow: ["error", { "builtinGlobals": true }]*/

function foo() {
    var Object = 0;
}

hoist

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hoist: functions

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/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let b = 6;
}

function b() {}

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/*eslint no-shadow: ["error", { "hoist": "functions" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
}

let a = 5;

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hoist: all

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/*eslint no-shadow: ["error", { "hoist": "all" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

hoist: never

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/*eslint no-shadow: ["error", { "hoist": "never" }]*/
/*eslint-env es6*/

if (true) {
    let a = 3;
    let b = 6;
}

let a = 5;
function b() {}

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allow

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/*eslint no-shadow: ["error", { "allow": ["done"] }]*/
/*eslint-env es6*/

import async from 'async';

function foo(done) {
  async.map([1, 2], function (e, done) {
    done(null, e * 2)
  }, done);
}

foo(function (err, result) {
  console.log({ err, result });
});

ignoreOnInitialization

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/*eslint no-shadow: ["error", { "ignoreOnInitialization": true }]*/

var x = x => x;

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/*eslint no-shadow: ["error", { "ignoreOnInitialization": true }]*/

var x = foo(x => x)

var y = (y => y)()

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