no-void
禁止 void 运算符
void 运算符接受一个操作数并返回 undefined：void expression 将评估 expression 并返回 undefined。它可以用来忽略 expression 可能产生的任何副作用：
¥The void operator takes an operand and returns undefined: void expression will evaluate expression and return undefined. It can be used to ignore any side effects expression may produce:
使用 void 运算符的常见情况是获取 “pure” undefined 值，因为在 ES5 之前，undefined 变量是可变的：
¥The common case of using void operator is to get a “pure” undefined value as prior to ES5 the undefined variable was mutable:
// will always return undefined
(function(){
return void 0;
})();
// will return 1 in ES3 and undefined in ES5+
(function(){
undefined = 1;
return undefined;
})();
// will throw TypeError in ES5+
(function(){
'use strict';
undefined = 1;
})();
另一种常见的情况是缩小代码，因为 void 0 比 undefined 短：
¥Another common case is to minify code as void 0 is shorter than undefined:
foo = void 0;
foo = undefined;
当与 IIFE（立即调用的函数表达式）一起使用时，void 可用于强制将 function 关键字视为表达式而不是声明：
¥When used with IIFE (immediately-invoked function expression), void can be used to force the function keyword to be treated as an expression instead of a declaration:
var foo = 1;
void function(){ foo = 1; }() // will assign foo a value of 1
+function(){ foo = 1; }() // same as above
function(){ foo = 1; }() // will throw SyntaxError
某些代码样式禁止 void 运算符，将其标记为不明显且难以阅读。
¥Some code styles prohibit void operator, marking it as non-obvious and hard to read.
规则详情
¥Rule Details
此规则旨在消除使用 void 运算符。
¥This rule aims to eliminate use of void operator.
此规则的错误代码示例：
¥Examples of incorrect code for this rule:
/*eslint no-void: "error"*/
void foo
void someFunction();
var foo = void bar();
function baz() {
return void 0;
}
选项
¥Options
此规则有一个对象选项：
¥This rule has an object option:
-
allowAsStatement设置为true允许将 void 运算符用作语句（默认false）。¥
allowAsStatementset totrueallows the void operator to be used as a statement (Defaultfalse).
allowAsStatement
当 allowAsStatement 设置为 true 时，规则不会在 void 运算符用作语句的情况下出错，即当它不用于表达式位置时，例如在变量赋值或函数返回中。
¥When allowAsStatement is set to true, the rule will not error on cases that the void operator is used as a statement, i.e. when it’s not used in an expression position, like in a variable assignment or a function return.
{ "allowAsStatement": true } 的错误代码示例：
¥Examples of incorrect code for { "allowAsStatement": true }:
/*eslint no-void: ["error", { "allowAsStatement": true }]*/
var foo = void bar();
function baz() {
return void 0;
}
{ "allowAsStatement": true } 的正确代码示例：
¥Examples of correct code for { "allowAsStatement": true }:
/*eslint no-void: ["error", { "allowAsStatement": true }]*/
void foo;
void someFunction();
何时不使用
¥When Not To Use It
如果你有意使用 void 运算符，则可以禁用此规则。
¥If you intentionally use the void operator then you can disable this rule.
相关规则
版本
此规则是在 ESLint v0.8.0 中引入。