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var name = null; var job; typeof name; //object typeof age;// undefined typeof job;// undefined
typeof e;// ReferhceError let e;
null表示一个空对象指针,所以用typeof检测null时返回"object",此外null === undefined总是返回true 所以没有必要把变量的值显式的设置为undefined
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初始化,类型注意点
Null注意点
null表示一个空对象指针,所以用typeof检测null时返回"object",此外null === undefined总是返回true
所以没有必要把变量的值显式的设置为undefined
The text was updated successfully, but these errors were encountered: