When I graduated from college and applied for a job, I used to do some bizarre interview questions. Here’s a trick question. It’s not really an interview question. You can use it to trick your programmer friends.
How to implement 2+2=5 in JavaScript?
Here are the answers.
Create a TXT file, change the suffix to.html, and open it in your browser.
< HTML > <script> g = function () {H = 3 return H + H} f = function () {degree = 2 return degree + H} // 3 + 3 = 6 alert(g()) // 2 + 2 = 5 alert(f()) </script> </html>Copy the code
Two dialog boxes will pop up successively, showing 6 and 5.
However, in the second function f, it is clear that H is assigned 2. 2 + 2 should be equal to 4. Why is the answer 5？？？？
Let’s use Chrome developer Tools to debug it and see what’s going on.
Why is it that f has two H’s that look exactly the same, but one has the value of 2 and one has the value of 3?
By now, the naked eye can’t help us. Here comes winHex, a hexadecimal file editing and disk editing magic.
A search for ASCII on Baidu shows that the hexadecimal code of uppercase H is 48.
Then we open the code file with WinHex, and sure enough we find the hexadecimal code of 48 with a capital H.
Similarly, the hexadecimal code for the plus sign “+” is 2B:
The space is 20.
So here’s the answer: the variable “H” in front of the plus sign that looks like a capital” H” to the naked eye isn’t actually AN “H.” It’s coded in hexadecimal CE 97. Its value is given 2 in f, and capital H is given 3, 2 + 3 = 5, so what we see in the popover is 5.
This question is not about closures in JavaScript.
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