[Solved] Jquery How do I update the data saved in a JSON file using JavaScript?

How do I update the data saved in a JSON file using JavaScript?

for example: If i have a JSON file called ‘person.json’, looking like:

{
  "Person": [
    {
      "Firstname": "John",
      "Lastname": "Doe"
    }
  ]
}

and I would like to append as new data set the name ‘John Smith’.
How could I do this using JavaScript?

EDIT:
Now I tried to use ‘fs.readFile()’ to read my JSON file.
The application I develop is a hybrid app using cordova.
If i use ‘fs.readFile()’ i get the error ‘Uncaught ReferenceError: fs is not defined’.
I tried to fix this problem by adding the line ‘var fs = Npm.require(‘fs’);’.
But this causes also an error: ‘Uncaught ReferenceError: Npm is not defined’

Is this error caused because npm is not available on a smartphone?
And how can i fix this problem?