Problem outputting nested stringified data to JSON.

In the current implementation of jsPsych, there is a problem handling trials with complex nested data. This is most easily illustrated in the jspsych-instructions plugin via the view_history property in trial_data.

The current solution implemented is to stringify the view_history array using { view_history: JSON.stringify(view_history)... }, which allows for sensible conversion to CSV. Without stringifying view_history, those view_history data would show up in the CSV as [object Object]. However, if you attempt to get the JSON data for the experiment, it cannot later be parsed with JSON.parse (or the json library in Python) due to problems resulting from attempting to parse a stringified JSON object within a stringified JSON object.

My current solution is to use the parse function from the json2csv library (available on npm) to replace the JSON2CSV helper function in jspsych.js. This allows me to have both sensible CSV and JSON representations of the data.

[jodeleeuw]

@becky-gilbert I went ahead and worked on this in the feature-objects-arrays-in-data branch.

It changes a core design idea: now we store objects and arrays in the data directly, instead of JSON versions of them. I updated all of the plugins that this affects, wrote a simple test to check the output of both .json() and .csv() methods in jsPsych.data, and updated the CSV conversion function.

Things that should probably happen before a merge:

• Add tests to the new test files for a few other plugins that generate arrays/objects in the data.
• Check the examples folder to see if any of the examples use JSON.parse() on data objects that are now not JSON.
• Check the docs to see what needs to be updated to reflect this change.

[stefanuddenberg]

Sorry for not seeing this sooner; Github does not do a good job of notifying me about activity on posts it would seem! That’s precisely the approach that I took in my own fork of the project; I’m using the json2csv library to handle the csv-ification of the jsPsych data.