圆括号运算符

概览

圆括号运算符( ) 用来控制表达式中的运算优先级.

语法

 ( )

说明

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 1st Edition. Standard Initial definition. Implemented in JavaScript 1.0
ECMAScript 5.1 (ECMA-262)
The Grouping Operator
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The Grouping Operator
Standard  

浏览器兼容性

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

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