How to save data in json or any other file format for the further use by JavaScript

i am trying to make a tracker application, which include the daily entry inside the file. what i am trying to do is, I want to save the data on some external file (each time i update the entry), so i can easily access data from that file every-time I open the application.

For example : if I am tracking the height of the plant i am growing, so i will use excel to store date and the height of the plant on the respective day and every time i open excel old data is there as well as i can also update new entries in the excel.

Is there any way to do this kind of thing in JavaScript. I am new to this stuff hope you can help me! looking forward to your suggestions.