Expression language: lookup equivalent for json arrays

I have a tag, say tableTag, which is of type Document: it's an array of json objects, all objects with the same structure. I'd like to define some more tags which are expression tags and get their value from tableTag looking up a value in a key of the tableTag objects That looks like looking up a value in a dataset, but whereas the expression language has a lookup function for datasets, I cannot seem to find an equivalent function for json arrays. I developed a python script function of my own, called jsLookup and it works. But if I want to use it in an expression tag, my project must be the Gateway Scripting Project and that's not possible.

Any suggestion, except going back to datasets?

Thanks, regards

There's no lookup equivalent, but I think an expression like {document}[indexOf({lookup})] might work? Subscripts and the indexOf function should both work on arrays and documents.

Sounds like a job for a utility module....