Boolean（''）为false和Boolean（new String（''））有什么区别？

Question

我怀疑两者都是字符串，为什么获取不同的布尔值 Boolean（''）为false和 Boolean（new String（''）） ？

Answer 1

Boolean函数为所有对象引用返回true。 new String("")创建一个字符串 object 。相反，""只是一个字符串基元。 Boolean返回false以获得空白字符串基元。

当作为函数（而不是构造函数）调用时，Boolean返回规范的ToBoolean abstract operation的结果：

抽象操作ToBoolean根据表9将参数转换为Boolean类型的值：

+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
|                 Table 9: ToBoolean Conversions                  |
+−−−−−−−−−−−−−−−+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| Argument Type | Result                                          |
+−−−−−−−−−−−−−−−+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| Undefined     | Return false.                                   |
+−−−−−−−−−−−−−−−+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| Null          | Return false.                                   |
+−−−−−−−−−−−−−−−+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| Boolean       | Return argument.                                |
+−−−−−−−−−−−−−−−+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| Number        | If argument is +0, −0, or NaN, return false;    |
|               | otherwise return true.                          |
+−−−−−−−−−−−−−−−+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| String        | If argument is the empty String (its length is  |
|               | zero), return false; otherwise return true.     |
+−−−−−−−−−−−−−−−+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| Symbol        | Return true.                                    |
+−−−−−−−−−−−−−−−+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
| Object        | Return true.                                    |
+−−−−−−−−−−−−−−−+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+

从表的最后一行可以看到，任何对象对象都将产生true。

Answer 2

1. 以下值被强制为false，因为它们是falsy值：''，NaN，undefined，null，{{1 }}。
2. 所有其他内容都将被强制使用0，因为它们是true值。

您要使用的功能：

truthy

并包含以下内容：

Boolean('') // Coercing a primitive empty string (falsy).