Debugger work in NodeJs || JAvaScriptFrameWork
Hello Friends and Welcome back
So I still have my debugger up and running
and now that I gave you a brief overlook of how it works, let's actually send another message here. Hit send,
it breaks again because I didn't remove the breakpoint
and let's now fix that error we have.
I showed you how we can navigate,
so let's click this line here or this button to move to the next line.
Now it registers this code and here you also see that it doesn't immediately execute this function because
if I click that button again, we jump to the end of this function here and that makes a lot of
sense because as I mentioned, this function is just registered by nodejs to be executed in the future
once the file is read.
So for now, code execution will continue with the other lines.
Now the problem we want to solve is not inside of here though
but if you want to get notified once a part in here is reached, you can simply add a breakpoint there,
resume execution and it will break once it reaches that,
so once that callback is triggered because the right file operation is done.
But our problem of course is the message,
right,
and the message is not available here anymore,
so this analysis is actually not useful to us.
So let's remove that breakpoint and resume and let's again run this one more time
and now let's not resume execution but look into message and we see message is message and that looks
wrong,
we see that parsed body is message equals and then our value.
Now since this is what we stored in the message constant, we now can tell pretty clearly that our error
has to be stemming from that part here because we clearly have our value in here
but then we seem to be extracting the wrong piece.
Now split also does its job and you can even use the console here to for example run some commands,
you can run parsed body split equal sign here and see what this returns,
so you see you get an array with message and tist because I mistyped test.
Now this clearly tells you
ok so split is working,
I'm in theory getting all the values I need,
so the only thing that can be wrong now is the value I'm extracting here and indeed we see that message,
holds message which is incorrect, message the first element in the array
so I seem to be extracting the wrong element from the array
and indeed we are extracting the first one when we should be extracting the second one here.
So let's now change it to a one
and now we get this error fixed.
Obviously this is a bit of a constructed example but this is just to show you how you can use the debugger
to go through your code step by step, that you have to keep in mind that node doesn't execute line after
line
but as I explained multiple times now that it registers callbacks which are executed sometime in the future
and which should therefore also have to control with breakpoints if you want to look into them.
And with that, you should have some powerful tools for finding and fixing errors in your code.
#NodeJS #JavaScriptFrameWork #CodingMaster