Question

I recently had an issue with some javascript that goes against every bone of my programming background. Javascript does this often to me, so I’m not that surprised.

I have a function as such…

function x(param1, booleanParam, arrayParam){
    ....
}

I was getting a runtime error saying that arrayParam.length was not defined. On debugging I saw this was true and went to find out why. Turns out I had forgotten a comma in my function call as such…

x(param1, true [arrayJunk]);

The problem I’m having is figuring out why this call was made at all? Why isn’t this a compile error, how does Javascript see this and think, “Yeah, that seems like it might work!”

Thanks in advance for any enlightenment you can share!

Answer 1

That’s an indexing expression.
It’s the same syntax as someArray[someIndex].

It will end up passing undefined as the second parameter too, unless arrayJunk happens to be the name of a property of boolean primitives.