JS function not recognised

Online experiments
1

URL of experiment: V1.1_shorttest_JS [PsychoPy]

Description of the problem:
I have the following JS code executed early on in the experiment (where ‘variability’ is specified via conditions in the Excel file):

function generateGaussian(mean, std) {
	var _2PI = Math.PI * 2;
	var u1 = Math.random();
	var u2 = Math.random();
	var z0 = Math.sqrt(-2.0 * Math.log(u1)) * Math.cos(_2PI * u2);
	var z1 = Math.sqrt(-2.0 * Math.log(u1)) * Math.sin(_2PI * u2);
	return z0 * std + mean;
}
function varInstance(variability, scaling, shift) {
gg = -999;
	do {
    gg = generateGaussian(0, variability);
	}
	while (-3 > gg > 3);
	return gg * scaling + shift;
}

Later on, the varInstance function is used in various bits of code throughout the experiment to define stimulus parameters, e.g.

widVar = varInstance(variability, 0.167, 1);

These then throw a ReferenceError: varInstance is not defined.

2

Try putting your function definitions in Before Experiment

or assigning them to a variable name

varInstance = function(variability, scaling, shift)
3

Thanks @wakecarter
I already had the function assigned to a variable name BUT I had not defined the function at before experiment (but at begin experiment).
I now moved that to Before Experiment, and when I try to synch the project, I get a Psychopy error:

Traceback (most recent call last):
  File “/Applications/PsychoPy.app/Contents/Resources/lib/python3.8/psychopy/app/builder/builder.py”, line 1381, in onPavloviaSync
  File “/Applications/PsychoPy.app/Contents/Resources/lib/python3.8/psychopy/app/pavlovia_ui/project.py”, line 741, in syncProject
  File “/Applications/PsychoPy.app/Contents/Resources/lib/python3.8/psychopy/app/pavlovia_ui/functions.py”, line 94, in showCommitDialog
  File “/Applications/PsychoPy.app/Contents/Resources/lib/python3.8/psychopy/projects/pavlovia.py”, line 1017, in getChanges
  File “/Applications/PsychoPy.app/Contents/Resources/lib/python3.8/psychopy/projects/pavlovia.py”, line 869, in repo
  File “/Applications/PsychoPy.app/Contents/Resources/lib/python3.8/psychopy/projects/pavlovia.py”, line 993, in configGitLocal
  File “/Applications/PsychoPy.app/Contents/Resources/lib/python3.8/psychopy/projects/pavlovia.py”, line 415, in user
  File “/Applications/PsychoPy.app/Contents/Resources/lib/python3.8/psychopy/projects/pavlovia.py”, line 144, in __init__
  File “/Applications/PsychoPy.app/Contents/Resources/lib/python3.8/requests/models.py”, line 900, in json
  File “json/__init__.pyc”, line 357, in loads
  File “json/decoder.pyc”, line 337, in decode
  File “json/decoder.pyc”, line 355, in raw_decode
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
4

Do you mean differently from how you showed the definition in your post?

I’m now wondering whether you have defined the same function twice and have an imbalance of brackets.

5

:thinking: I think I am being thick then.
When you wrote

varInstance = function(variability, scaling, shift)

Did you mean to literally use ‘function’?
I took it to mean that I name my function varInstance, and then call that function when I want to use it to assign variables, as in

6

I meant literally as per my older crib sheet when defining the function, not when calling it.

7

Hmm. So I found the problem (I had used var as a variable name, not realising that this is a JS command), and the other SNAFUs were associated with missing brackets

But I also used your suggestion of how to define the function and that led to errors (the function name not being recognised). What is strange is that I copied and pasted code to this effect from working JS experiment authored by a colleague and it also produced the error. but, main thing is that it is working now!

8

Update to previous post: I have figured out that if you want to use the format

varInstance = function(variability, scaling, shift)

then this cannot be in the "before experiment’ tab. It has to be in the ‘begin experiment’ tab

9

Sorry I hadn’t made that aspect clear. That was why I linked to both versions of my crib sheet. The Before Experiment tab didn’t exist in 2020.