全局范围内的console.log（！status）产生意外结果 [英] console.log(!status) in global scope producing unexpected result

问题描述

进入一个有趣的问题。我正在努力尝试切换分配给变量的布尔值。它没有用，最终我尝试了这段代码。

Ran into an interesting issue. I was working on trying to toggle a boolean that was assigned to a variable. It wasn't working and eventually I tried this code.

var status = false;
console.log(!status);

我希望它能提供 true 控制台，但我得到 false 。我认为javascript会首先在括号内运行代码以找到它的值，然后在console.log中运行该值。你能解释一下为什么我在控制台中没有得到 true 值吗？

I expected it to provide true in the console, but instead I got false. I figured that javascript would run the code inside the parenthesis first to find it's value and then console.log the value. Could you please explain why I am not getting a true value in the console?

推荐答案

window.status 已经存在（它用于获取/设置浏览器状态栏的文本），当为其分配值时，它将转换为字符串。如果你执行 console.log（status）; ，你会看到 status 的字符串值false，这会导致您看到输出 false ，因为您实际上有！false和false是JavaScript中的真值。

window.status already exists (it is used to get/set the text of the browser's status bar) and when a value is assigned to it, it is converted to a string. If you do console.log( status ); you will see that status has the string value "false", which causes you to see the output false, since you effectively have !"false" and "false" is a truthy value in JavaScript.

如果你在函数中做同样的事情，你会得到预期的输出：

If you do the same thing inside a function you'll get the expected output:

(function ( ) {
  var status = false;
  console.log(!status); // true
})();

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