arrow-parens

箭头函数参数需要括号

一些该规则报告的问题可以通过 --fix 命令行选项 自动修复

箭头函数只有一个参数时可以省略括号。在所有其他情况下，参数必须用括号括起来。此规则强制在箭头函数中一致地使用括号。

规则详情

此规则在箭头函数参数周围强制使用括号，而不考虑数量。例如：

/*eslint-env es6*/

// Bad
a => {}

// Good
(a) => {}

遵循这种风格将帮助您找到箭头函数 (=>)，当以 >= 之类的比较为目的时，这些箭头函数可能会被错误地包含在条件中。

/*eslint-env es6*/

// Bad
if (a => 2) {
}

// Good
if (a >= 2) {
}

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/*eslint-env es6*/

// Bad
(a) => {}

// Good
a => {}

选项

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2FKeCwRi48MyVF6DOWYB5b6fwS9ofR5/6OWB4UuEKr8=

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RHcFcqcdjTptb3VLhipq+FbijyMY7LKSldeWqna+uuyrnrqB+qnh/vITDyCmnfLhz4MfpnbwsyolliA60y1Q2Q==

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always

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/*eslint arrow-parens: ["error", "always"]*/
/*eslint-env es6*/

a => {};
a => a;
a => {'\n'};
a.then(foo => {});
a.then(foo => a);
a(foo => { if (true) {} });

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/*eslint arrow-parens: ["error", "always"]*/
/*eslint-env es6*/

() => {};
(a) => {};
(a) => a;
(a) => {'\n'}
a.then((foo) => {});
a.then((foo) => { if (true) {} });

如果语句

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/*eslint-env es6*/

var a = 1;
var b = 2;
// ...
if (a => b) {
 console.log('bigger');
} else {
 console.log('smaller');
}
// outputs 'bigger', not smaller as expected

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/*eslint-env es6*/

var a = 1;
var b = 0;
// ...
if ((a) => b) {
 console.log('truthy value returned');
} else {
 console.log('falsy value returned');
}
// outputs 'truthy value returned'

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/*eslint-env es6*/

var a = 1, b = 2, c = 3, d = 4;
var f = a => b ? c: d;
// f = ?

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dUXTMCrJ8lP0buAurfHQNqCCzqHOOvUqWmuG3K28dmo=

/*eslint-env es6*/

var a = 1, b = 2, c = 3, d = 4;
var f = (a) => b ? c: d;

as-needed

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/*eslint arrow-parens: ["error", "as-needed"]*/
/*eslint-env es6*/

(a) => {};
(a) => a;
(a) => {'\n'};
a.then((foo) => {});
a.then((foo) => a);
a((foo) => { if (true) {} });
const f = /** @type {number} */(a) => a + a;
const g = /* comment */ (a) => a + a;
const h = (a) /* comment */ => a + a;

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/*eslint arrow-parens: ["error", "as-needed"]*/
/*eslint-env es6*/

() => {};
a => {};
a => a;
a => {'\n'};
a.then(foo => {});
a.then(foo => { if (true) {} });
(a, b, c) => a;
(a = 10) => a;
([a, b]) => a;
({a, b}) => a;
const f = (/** @type {number} */a) => a + a;
const g = (/* comment */ a) => a + a;
const h = (a /* comment */) => a + a;

requireForBlockBody

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/*eslint arrow-parens: [2, "as-needed", { "requireForBlockBody": true }]*/
/*eslint-env es6*/

(a) => a;
a => {};
a => {'\n'};
a.map((x) => x * x);
a.map(x => {
  return x * x;
});
a.then(foo => {});

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/*eslint arrow-parens: [2, "as-needed", { "requireForBlockBody": true }]*/
/*eslint-env es6*/

(a) => {};
(a) => {'\n'};
a => ({});
() => {};
a => a;
a.then((foo) => {});
a.then((foo) => { if (true) {} });
a((foo) => { if (true) {} });
(a, b, c) => a;
(a = 10) => a;
([a, b]) => a;
({a, b}) => a;