Indeed.   “HTML plus JQuery is not merely a file:   it is a computer program.   To (merely) describe it to u as “consisting of certain numbers” strongly implies that the “numbers” actually reside somewhere else ... a database, perhaps? ... and that this “HTML plus JQuery” that you have is, in effect, the source-code to a computer program that obtains and displays the data (from somewhere).

Step back, please, and describe the entire problem to us as best you can.   What is this web-page?   Can we see it somewhere on the web?   What is the nature of the file that describes the “modifications” that you wish to do, and what sort of modifications are they?

What you have now is what is called an XY Problem.   This is undoubtedly not a “file parsing” task at all.   We are happy to help you to get on the right track with this, and to get it done.