Html Array/Variable from text file

Hello everybody
I’m quite new to programming and have following problem:
I have html code for the OpenStreetMap that shows markers on the map. The marker positions are set in the index.html file but I would like to extract them from a text file instead. Also there are another 3 variables I would like to set in a text file.
Can somebody show me how this is done? Do I need js for this? How would that be done?
Thanks a lot in advance.

Entire html code:
pasted . co / efd523cd

Variables I would like to have in a separate text file
pasted . co / baaf9612

you can use .json file to save your data and it is easily readable