Reassignment operators and post-increment

Question

I'm toying with a timed JavaScript Challenge and want to make sure I understand this correctly.

var x = 0;
for(; x < 2; x++) {
x += x - x++;
}

console.log(x);

// Output is 2

1.) If x is less than 2, keep going.
2.) x += x(0) - x++(0), x now equals 0.
3.) Increment x by 1.
4.) x is less than 2, keep going.
5.) x += x(1) - x++(1), x now equals 1.
6.) Increment x by 1.
7.) x is not less than 2, exit out of the loop.

Am I understanding this right?

Answer 1

1. You can add console log at beginning of for loop and end of for loop to check the change of variable in each iteration. Like this:
https://code.sololearn.com/W6Nf9QAk71xP/?ref=app

2. The increment of x++ in x += line is not effective because after it increments x, x is replaced by (original x+0)

Answer 2

Gordon Thank you, that's interesting! I really appreciate it!

Answer 3

In your new code,
The reason that your for loop run only once is because when you z = x++, x is already incremented by 1 after z is 0, so you can see in the iteration, pre x is 1 already.

The reason that post y and post z is 0 is, because they are assigned before for loop, y stores value of x which is 0, z also stores value of z which is 0.

And in the for loop, they are called as value, especially z, it is not behaving as x++ in the for loop.

Your original intention, if I have not misunderstand you, should be like this :

https://code.sololearn.com/Wz6Yu57Th04c/?ref=app

Notice the use anonymous function to execute the update of x every time when the function z is called.

Answer 4

You are welcome, DumbledoresArmy.

Please allow me to emphasize the use of console log during the process of functions in debugging.

This is a demo I coded for another Q&A to explain how to find out bug.

https://code.sololearn.com/WuBzocc861ZK/?ref=app

By the way, I am a Harry Potter fans too

Answer 5

I used console.log in my own test code but my specific question was if the math right of the equal sign was always equal to 0 or if something else was happening.

I'm not debugging because this is a challenge question I am trying to follow through.

https://code.sololearn.com/WnAsePgfjJBv/?ref=app

Answer 6

Gordon, that's it, I'm naming my patronus after you! 😊

Answer 7

🤣🤣🤣🤣🤣
Expecto Patroooonum! 🧙‍♂️