undefined == false
时间: 2023-10-08 20:09:59 浏览: 54
The expression `undefined == false` is a comparison between the value `undefined` and the value `false`. In JavaScript, when comparing values using the `==` operator, type coercion can occur, which means that values of different types may be converted to a common type in order to perform the comparison.
In this case, the value `undefined` is of the type `undefined`, while the value `false` is of the type `boolean`. When these two values are compared using the `==` operator, they are not of the same type, so type coercion occurs.
The rules for type coercion in JavaScript can be complex, but in general, `undefined` is coerced to `NaN` (which stands for "Not a Number"), and `false` is coerced to `0`. Therefore, the expression `undefined == false` is equivalent to `NaN == 0`, which is false because `NaN` is not equal to any value, including `0`.
It is generally recommended to use the `===` operator for comparisons in JavaScript, as it does not perform type coercion and only returns true if the values being compared are of the same type and have the same value.
相关推荐
![pdf](https://img-home.csdnimg.cn/images/20210720083512.png)
![pdf](https://img-home.csdnimg.cn/images/20210720083512.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)