my solution to this was to put data into a .JS file as a variable (using backend s/w - like VBA/Excel).
And also in other longstanding instances, use existing .HTM files (4 in succession).
Then process the variable (or .innerHTM's) and re-load the results into the IFRAME via .innerHTM
this works over the internet on all browsers I can test with (including Android OS) for files on the same domain. However there are issues for a system using local files (to the PC) with Chrome, & presumably Chrome based browsers like Opera. FireFox and IE seem to handle locally.
In a more recent project which was to reside on an Android phone, it was found that writing back to the IFRAME didn't work, and the reason was never determined. The post processing of the data was written to a
layer (.innerHTM). The IFRAME was re-loaded many times from a suite of .htm files.
Only FireFox on Android (from local files) worked. Chrome did not handle it.
An attempt was made to load .txt files into an IFRAME which never seemed to work fully locally, even in FireFox.