Ole-Morten Duesund e8428de775 Add progressive web app companion for cross-platform access

Vite + TypeScript PWA that mirrors the Android app's core features:
- Pre-processed shelter data (build-time UTM33N→WGS84 conversion)
- Leaflet map with shelter markers, user location, and offline tiles
- Canvas compass arrow (ported from DirectionArrowView.kt)
- IndexedDB shelter cache with 7-day staleness check
- Service worker with CacheFirst tiles and precached app shell
- i18n for en, nb, nn (ported from Android strings.xml)
- iOS/Android compass handling with low-pass filter
- Respects user map interaction (no auto-snap on pan/zoom)
- Build revision cache-breaker for reliable SW updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

2026-03-08 17:41:38 +01:00

6.3 KiB

Raw Blame History

Node.js - jsonfile

Easily read/write JSON files in Node.js. Note: this module cannot be used in the browser.

Why?

Writing JSON.stringify() and then fs.writeFile() and JSON.parse() with fs.readFile() enclosed in try/catch blocks became annoying.

Installation

npm install --save jsonfile

API

readFile(filename, [options], callback)
readFileSync(filename, [options])
writeFile(filename, obj, [options], callback)
writeFileSync(filename, obj, [options])

readFile(filename, [options], callback)

options (object, default undefined): Pass in any fs.readFile options or set reviver for a JSON reviver.

throws (boolean, default: true). If JSON.parse throws an error, pass this error to the callback. If false, returns null for the object.

const jsonfile = require('jsonfile')
const file = '/tmp/data.json'
jsonfile.readFile(file, function (err, obj) {
  if (err) console.error(err)
  console.dir(obj)
})

You can also use this method with promises. The readFile method will return a promise if you do not pass a callback function.

const jsonfile = require('jsonfile')
const file = '/tmp/data.json'
jsonfile.readFile(file)
  .then(obj => console.dir(obj))
  .catch(error => console.error(error))

readFileSync(filename, [options])

options (object, default undefined): Pass in any fs.readFileSync options or set reviver for a JSON reviver.

throws (boolean, default: true). If an error is encountered reading or parsing the file, throw the error. If false, returns null for the object.

const jsonfile = require('jsonfile')
const file = '/tmp/data.json'

console.dir(jsonfile.readFileSync(file))

writeFile(filename, obj, [options], callback)

options: Pass in any fs.writeFile options or set replacer for a JSON replacer. Can also pass in spaces, or override EOL string or set finalEOL flag as false to not save the file with EOL at the end.

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj, function (err) {
  if (err) console.error(err)
})

Or use with promises as follows:

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj)
  .then(res => {
    console.log('Write complete')
  })
  .catch(error => console.error(error))

formatting with spaces:

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj, { spaces: 2 }, function (err) {
  if (err) console.error(err)
})

overriding EOL:

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj, { spaces: 2, EOL: '\r\n' }, function (err) {
  if (err) console.error(err)
})

disabling the EOL at the end of file:

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj, { spaces: 2, finalEOL: false }, function (err) {
  if (err) console.log(err)
})

appending to an existing JSON file:

You can use fs.writeFile option { flag: 'a' } to achieve this.

const jsonfile = require('jsonfile')

const file = '/tmp/mayAlreadyExistedData.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj, { flag: 'a' }, function (err) {
  if (err) console.error(err)
})

writeFileSync(filename, obj, [options])

options: Pass in any fs.writeFileSync options or set replacer for a JSON replacer. Can also pass in spaces, or override EOL string or set finalEOL flag as false to not save the file with EOL at the end.

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFileSync(file, obj)