Javascript to filter values from embedded field and then select random item

Kia ora koutou, hello everyone! I have an embedded field 'colour_selection' which is populated with answers from a multiple answer questions in the survey flow. I would like to use Javascript to filter out specific answers, and then from the filtered list take a random answer to store back in to an embedded field to pipe in to a following question. (I would have loved to do this using a loop and merge, but it seems like it's not possible to exclude answers easily). I have limited Javascript ability, but have managed to get this code to work fine here https://jsfiddle.net/1etL6axn/ However when I try to run this in Qualtrics I'm getting a console error "colourSelection.filter is not a function". I get an "access denied" error when I try to post code here, so here is a screenshot. And I've attached the qsf. ! Is this a limitation within Qualtrics? Should I try to find a solution using JQuery instead? Have I missed something unique to Qualtrics to make this work? Thanks in advance Dan