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eztxt4fs

Ambidextrous sugar for reading and writing text files via the fs module.

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eztxt4fs

Ambidextrous sugar for reading and writing text files via the fs module found in nodejs, Electron, and react-native. Especially useful for loading and saving data like user preferences and other not-enormous data in OS-conventional locations.

Installation

  1. npm install --save eztxt4fs

Examples

Attempts to read a file located at /Users/barney/myFile.json:

var Textfile = require('eztxt4fs');

Textfile.read('/Users/barney/myFile.json')
.then(function(data) {
    // data == JSON.parse(file contents) || undefined
});

Attempts to store an object as a file located at /Users/barney/someObject.json:

var Textfile = require('eztxt4fs');

var data = {
    letters: ['a','b','c'],
    number: 5
};

Textfile.write('/Users/barney/someObject.json', data)
.then(function() {
    // it's done
});

Documentation

Textfile.read( path [, options] )

Attempts to read the contents of a file:

  • if the file doesn't exist, returns undefined
  • attempts to parse as JSON (unless options.json = false)
  • will throw if Textfile configured for JSON but file contents not well-formed

When calling .read() on an instance, do not supply path:

  • instance.read( [options] )

Textfile.write( path [, value [, options]] )

Attempts to write value to disk at the specified path.

  • will create directories if necessary
  • can throw permissions-related errors while creating files and directories
  • will throw if Textfile configured for JSON but value cannot be serialized

When calling .write() on an instance, do not supply path:

  • instance.write( [value [, options]] )

Warning: Textfile.write() with no arguments will erase the contents of your file, regardless of configuration.

  • Writing undefined to a JSON-configured file will write the word undefined to the file, which this library will re-interpret as undefined upon read, but which other libraries are likely to reject, because JSON.parse("undefined") throws in a vanilla JS environment.

Note: this behavior will be better-defined soon. Expect the current behavior to change.

new Textfile( path [, options] )

Returns a new, configured Textfile. Does not perform any filesystem operations.

Once a Textfile has been configured, it can be read from and written to as described above. The options set at creation can be overridden in any subsequent call, but such overrides apply to a single operation only.

path cannot be changed after creation.

options

All Textfile calls accept an options argument. The following properties and values modify Textfile's behavior:

NameTypeDefaultDescription
asyncBooleantruewhether filesystem operations should be asynchronous; see Async
encodingString'utf8'file encoding
jsonBooleantruewhether file contents should be JSON-encoded
replacerFunction or Arraynullif options.json, passed to JSON.stringify(value, replacer, space) when writing
spaceNumber or Stringnullif options.json, passed to JSON.stringify(value, replacer, space) when writing
reviverFunctionnullif options.json, passed to JSON.parse(string, reviver) when reading

Any additional properties will be passed down to the core nodejs methods, thus:

  • FS.readFile(path, additionalProperties, callback)
  • FS.readFileSync(path, additionalProperties)
  • FS.writeFile(path, string, additionalProperties, callback)
  • FS.writeFileSync(path, string, additionalProperties)
  • FS.mkdir(path, additionalProperties, callback)
  • FS.mkdirSync(path, additionalProperties)

Async

Textfile's read and write methods are ambidextrous, meaning that they can be invoked in a blocking or non-blocking style as circumstances require.

By default, Textfile.read() & Textfile.write() operate asynchronously, and therefore return promises. However, if options.async = false, these methods will block until they can provide their return values. This is useful for e.g. writing data to disk when an Electron app is closing, under which circumstances async file operations are not guaranteed to complete before exit.

Note: Textfile creation is always synchronous.

async can be set at creation time, and temporarily overridden at any call site.

var Textfile = require('eztxt4fs');

// default configuration is async
var userPrefs = new Textfile(`~/Library/Preferences/MyApp/user1.myapp-settings`);

// read and write prefs asynchronously
var prefUpdatePromise = userPrefs.read()
.then(function(prefData) {
    var newPrefs = Object.assign({}, prefData, { updated: true });
    return userPrefs.write(newPrefs);
});

// read and write same prefs synchronously
var prefData = userPrefs.read({ async: false });
var newPrefs = Object.assign({}, prefData, { updated: true });
userPrefs.write(newPrefs, { async: false });

Static & instance-based invocation supported

You can read and write files without creating objects:

var Textfile = require('eztxt4fs');

function readPersonFile(filingName) {
    var filename = filingName + '.person';
    return Textfile.read(filename);
}

function writePersonFile(person) {
    var filename = person.filing_name + '.person';
    return Textfile.write(filename, person);
}

Instances created with new preserve their original path and options, allowing for succinct reads and writes.

var Textfile = require('eztxt4fs');

var prefs = new Textfile('myapp.prefs');

function getPrefs() {
    return prefs.read();
}

function setPrefs(newPrefs) {
    return prefs.write(newPrefs);
}

Supported Platforms

  • node
  • Electron
  • react-native

Caveats

  • Has not been tested on Windows.
  • Has not been tested in react-native (neither iOS nor Android).
  • Has not been tested against an NTFS filesystem.

I think eztxt4fs will work as advertised in all of these cases, but haven't tested them yet. If you find out, please post an issue with your results.

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