Javascript bug

[neutralizer]

I'm really lost on this homework on Javascript and I call upon the mighty programming gurus of AT for help. The point of the function is to output "100 101 102." In Java or C++, the code would normally output "100 101 102," but in Javascript it outputs "100 101 101." I know how to fix the code to output properly, but I don't know why.

 

[Gunslinger08]

Try passing in the object and the function separately to functionExecutor. Like this:
functionExecutor(obj, inc)

function functionExecutor(obj, fnc)
{
obj.fnc();
}

 

[neutralizer]

Originally posted by: joshsquall
Try passing in the object and the function separately to functionExecutor. Like this:
functionExecutor(obj, inc)

function functionExecutor(obj, fnc)
{
obj.fnc();
}

No, I know how to fix it. Although what you suggested doesn't work, you have to do fnc.call(obj); What I'm asking is why it prints "100 101 101" in Javascript.

 

[Gunslinger08]

Originally posted by: neutralizer

Originally posted by: joshsquall
Try passing in the object and the function separately to functionExecutor. Like this:
functionExecutor(obj, inc)

function functionExecutor(obj, fnc)
{
obj.fnc();
}

No, I know how to fix it. Although what you suggested doesn't work, you have to do fnc.call(obj); What I'm asking is why it prints "100 101 101" in Javascript.

It's passing the object by value, not reference. It is incrementing the value inside of the functionExecutor, but that isn't stored in the same memory location as the original obj. Try printing the value inside functionExecutor after you increment it. Should say 102.

 

[neutralizer]

Thanks for the help, joshsquall. I have another homework problem in which there is an error in the code that can be fixed by editing a line. I know that in order to fix it, it should be Stack.prototype.top = blah, but I don't see the difference between methods defined in the function Stack and methods defined by adding a property top to Stack that points to a function.

 

[GundamSonicZeroX]

You have a JavaScript class. I'm so jealous.

 

[neutralizer]

Originally posted by: GundamSonicZeroX
You have a JavaScript class. I'm so jealous.

It's actually a class on compilers, but the languages we're working on is Javascript and AJAX.

 

[jman19]

Originally posted by: neutralizer

Originally posted by: GundamSonicZeroX
You have a JavaScript class. I'm so jealous.

It's actually a class on compilers, but the languages we're working on is Javascript and AJAX.

A compilers class taught using Javascript? 😕

 

[neutralizer]

Originally posted by: jman19

Originally posted by: neutralizer

Originally posted by: GundamSonicZeroX
You have a JavaScript class. I'm so jealous.

It's actually a class on compilers, but the languages we're working on is Javascript and AJAX.

A compilers class taught using Javascript? 😕

Actually, it's a programming languages and compilers class. I do agree with your confusion on how a compilers class can be taught with Javascript since the language is interpreted rather than compiled.

 

[jman19]

Originally posted by: neutralizer

Originally posted by: jman19

Originally posted by: neutralizer

Originally posted by: GundamSonicZeroX
You have a JavaScript class. I'm so jealous.

It's actually a class on compilers, but the languages we're working on is Javascript and AJAX.

A compilers class taught using Javascript? 😕

Actually, it's a programming languages and compilers class. I do agree with your confusion on how a compilers class can be taught with Javascript since the language is interpreted rather than compiled.

Ah well I guess if you are doing a survey of sorts of programming languages then it makes a lot more sense that you are using Javascript.

 

[CTho9305]

functionExecutor(obj.inc); // execute obj.inc

That literally passes the function, so functionExecutor sees "this.value++", so it increments the value property of whatever "this" happens to be. Note that in other languages, that may actually do functionExecutor(obj.inc()), running .inc() and passin the (bogus) result to functionExecutor.

You could do functionExecutor(function() { obj.inc(); }); if you wanted to... that would cause obj.inc() to be executed from within functionExecutor.

 

[troytime]

Originally posted by: neutralizer

Originally posted by: GundamSonicZeroX
You have a JavaScript class. I'm so jealous.

It's actually a class on compilers, but the languages we're working on is Javascript and AJAX.

I hope...seriously, that your instructor didn't tell you that AJAX is a language.