问题描述
根据ECMAScript规范，既（！）和的使用的，而不是运营商也做了一些检查，以扭转结果。那么，为什么是双逻辑非操作中的布尔（）功能？
According to the ECMAScript specification, both the unary logical NOT operator (!) and the Boolean() function use the internal function ToBoolean(), and the NOT operator also does a few checks to reverse the result. So why is a double logical NOT operation much faster than running the Boolean() function?
我用下面这段code，以测试这是更快的：
I used the following piece of code to test which was faster:
function logicalNotOperator() {
var start = performance.now();
for (var i = 0; i < 9999999; i++) !!Math.random();
return 0.001 * (performance.now() - start);
}
function booleanFunc() {
var start = performance.now();
for (var i = 0; i < 9999999; i++) Boolean(Math.random());
return 0.001 * (performance.now() - start);
}
注意：我不是指新布尔（）的构造，但布尔（）功能，它可以强制将它交给一个布尔的说法。
Note: I am not referring to the new Boolean() constructor, but the Boolean() function that coerces the argument it's given to a boolean.
推荐答案
在布尔将调用函数（内部优化），最即时编译器将内联双不使用XOR远远快（来源$ C $ C参考 - JägerMonkey）
While Boolean will call the function (internally optimized), most JITs will inline the double not to use XOR which is far faster (source code reference - JägerMonkey).
而JSperf：
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