Data Persistence for DUMMIES

it gives you a magical javascript object that persists changes even after restart, and you can watch for changes too!

both Node.js and Browser environment are supported.

Quick Guide:

//get the magical object
import Fson from 'fson-db';
const starwars = Fson('./file/path');

// save data
starwars.owner = 'Disney';
starwars.movies = [
  {
    title: 'A New Home',
    date: new Date(1997, 5, 25),
    directory: {
      name: 'George Locas',
    }
  },
  {
    title: 'The Force Awakens',
    date: new Date(2015, 12, 18),
    directory: {
      name: 'J.J. Abraham',
    }
  },
]
//read data just like regular js object
const filtered = starwars.movies.filter(it => it.date.getUTCFullYear() > 2012);
console.log(`${filtered.length} movies since ${starwars.owner}`)

//watch for changes
import {watch} from 'fson-db';
watch(starwars,(field,newValue,oldValue) => {
  if (field === 'owner') {
    console.log(`${newValue} is the new boss here!`)
  }
  if (field === 'movies') {
    console.log(`a new movie has been released!`)
  }
})

---

How does it work?

fson-db load object from DataStorage, keep a copy of object in memory and apply effects to DataStorage.

DataStorage saves data with JSON format in LocalStorage for Browsers and FileSystem for Node.JS.

the following apis are supported, full js object apis support is in progress.

Full Example:

//browser
import Fson from 'fson-db';

//Node.js
const Fson = require('fson-db');

//specify a directory path
const dbPath = './config';

//db is a js object! but any changes to in will be persistent!
//dbPath is only required for Node.js
const db = Fson(dbPath); //db must be a constant!

//save any type of literals
db.name = 'john doe';
db.age = 24;
db.pi = 3.1415;
db.isActive = true;
db.date = new Date();

//fetch literals
console.log(db.name) // john doe
console.log(db.age) //  24
console.log(db.pi) //  3.1415
console.log(db.isActive) //  true
console.log(db.date) //  "1997-02-19T20:30:00.000Z"


//save objects!
db.object = {
  foo: 'bar',
}

//fetch objest and nested fields
console.log(db.object); // { foo:"bar" }
console.log(db.object.foo); // bar

//modify nested objects
db.object.foo = 'rab';
console.log(db.object.foo); // rab


//save arrays!
db.numbers = [1, 2, 3, 4, 5, 6];

//modify arrays!
db.numbers = db.numbers.filter(i => i % 2 == 0);
console.log(db.numbers); // [ 2, 4, 6 ]

//push to arrays
db.numbers.push(8, 10, 12);
console.log(db.numbers); // [ 2, 4, 6, 8, 9, 10 ]

//save array of objects
db.users = [{id: 1}, {id: 2}]
console.log(db.users[0].id); // 1
console.log(db.users.length); // 2

//modify with indexes!
db.users[1] = {id: 3}
console.log(db.users[1].id); // 3

Loop through entries

//list entries with Object.keys
db.obj = {
  one: 'the_one',
  two: 'the_two',
  three: 'the_three',
};
console.log(Object.keys(db.obj)) // ['one', 'two', 'three']

//loop through object keys
for (const key in db.obj) {
  const value = db.obj[key];
  console.log(`${key}: ${value}`);
}

for (const [key, value] of Object.entries(db.obj)) {
  console.log(`${key}: ${value}`);
}


//the above example also works for nested objects

Delete Operator

db.obj = {};
delete db.obj;
console.log(typeof db.obj) // 'undefined'

//nested objects!
db.obj = {
  nested: {},
};
delete db.obj.nested;
console.log(typeof db.obj.nested) // 'undefined'

Note: high performance is not a priority for now, everything is synchronous, so use db inside async functions