“真实"的结果和“虚假"在 JavaScript 中令人困惑 [英] Results of "truthy" and "falsey" is confusing in JavaScript

问题描述

我正在学习 JavaScript 基础知识.我对真实"和虚假"的结果感到困惑.谁能告诉我这是什么原因?

I am learning JavaScript basics. I am confused about the results of "truthy" and "falsey". Can anyone tell the reason for this?

myVariable = undefined ? "truthy" : "falsey";

结果是falsey".

myVariable = typeOf someUndefinedVariable ? "truthy" : "falsey";

结果是真实".

我期望第二个结果为falsey".为什么我得到了真相"?我真的很困惑.

I expected "falsey" instead for the second result. Why did I get "truthy"? I am really confused.

推荐答案

typeof 返回值的类型 name，它总是一个非空字符串.非空字符串真实.

typeof returns the type name of the value, which is always a non-empty string. A non-empty string is truthy.

> typeof someUndefinedVariable
"undefined"
> typeof (typeof someUndefinedVariable)
"string"
> Boolean("undefined")
true

另见 JavaScript 中的所有假值

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