jsPsych code runs on local server but not when inside JATOS

[amunn]

I have a jsPsych experiment which has some browser checking code I wrote. This code works find running the jsPsych code locally or on cognition.run, but when I try to run the same code through a JATOS server it fails.

In the code I define an isBrowser function. (full code is here)

function isBrowser(name) {
    return navigator.userAgent.toLowerCase().indexOf(name) != -1;
}

When I run the experiment through JATOS I get the following error:

Uncaught (in promise) TypeError: isBrowser is not a function

Is there something about wrapping the jsPsych code in the jatos wrapper that causes this? If so, how do I fix it?

(As a workaround, I can use the browser-check plugin, but I'd like to understand the problem more generally, since it seems to be related to how functions work, not this particular function.)

[jodeleeuw]

Hi @amunn,

This sounds like a scoping issue but I think we'd need to see the context of where the isBrowser function is defined and how the script(s) are loaded when running through JATOS. I don't think the code you've linked to shows where the function is defined relative to the context.

[becky-gilbert]

Hi @amunn, just to add to Josh's response about this being a scoping issue: I'm guessing the reason you might be having scoping problems that only occur with JATOS is because of the addition of the jatos.onLoad function. This function can change the scope and availability of different variables, depending on where you put it. If you haven't done so already, I would try putting all of your code inside the jatos.onLoad function and see if that works.

If you'd like more guidance/explanation, feel free to post more code as Josh suggested so that we can see where the function is created and called. You may also be interested in reading posts about JavaScript scope, such as this one and this one.