Grouping
圆括号运算符( )?用来控制表达式中的运算优先级.
语法
( )描述
圆括号运算符由一对圆括号组成,包裹表达式和子表达式用来覆盖常规的?运算符优先级?,达到低优先级的表达式比高优先级的表达式更早运算.
示例
下面的代码展示了加法运算先于乘法运算的情况.
var a = 1;
var b = 2;
var c = 3;
// default precedence
a + b * c // 7
// evaluated by default like this
a + (b * c) // 7
// now overriding precedence
// addition before multiplication
(a + b) * c // 9
// which is equivalent to
a * c + b * c // 9规范
Specification | Status | Comment |
|---|---|---|
ECMAScript Latest Draft (ECMA-262)The definition of 'The Grouping Operator' in that specification. | Living Standard | ? |
ECMAScript 2015 (6th Edition, ECMA-262)The definition of 'The Grouping Operator' in that specification. | Standard | ? |
ECMAScript 5.1 (ECMA-262)The definition of 'The Grouping Operator' in that specification. | Standard | ? |
ECMAScript 1st Edition (ECMA-262)The definition of 'The Grouping Operator' in that specification. | Standard | Initial definition. Implemented in JavaScript 1.0. |
浏览器兼容性
Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Edge | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
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