Writing Array to external file when new marker is created

[BrienB]

I am developing a Leaflet map that will be running offline on a device using chromium (a BrightSign).  I am currently using an external javascript file to store my marker data (that I manually entered), which is used to create and show my markers on the map when the page is loaded.  Now, I need to find a way to store marker data to the same external file when I create a new marker.  I am able to append the existing array by pushing the new marker data to the array and view the appended array in the console log.  Now, I just need to store the data.  The external file doesn't necessarily have to be a javascript file.  Any ideas are greatly appreciated.