@mojule/memory-fs NPM

memory-fs

A simple in-memory filesystem. Holds data in a javascript object.

Forked from memory-fs in order to allow promisifying the functions, see Changes below

const MemoryFS = require( '@mojule/memory-fs' )
const fs = MemoryFS()

fs.mkdirpSync( '/a/test/dir' )
fs.writeFileSync( '/a/test/dir/file.txt', 'Hello World' )
fs.readFileSync( '/a/test/dir/file.txt' ) // returns Buffer( "Hello World" )

// Async variants too
fs.unlink( '/a/test/dir/file.txt', err => {
  // ...
})

fs.readdirSync( '/a/test' ) // returns [ 'dir' ]
fs.statSync( '/a/test/dir' ).isDirectory() // returns true
fs.rmdirSync( '/a/test/dir' )

fs.mkdirpSync( 'C:\\use\\windows\\style\\paths' )

Options

You can patch the API by passing options - MemoryFS is missing many functions from fs, you can add them as needed, or you can add custom functions

Patch functions have the same signature as the original function except for taking an additional first argument, fs - this object contains all of the existing functions and the data property that holds the backing store

const MemoryFS = require( '@mojule/memory-fs' )

// when called on `fs` instance the signature will be isEmptyFileSync( path )
const isEmptyFileSync = ( fs, path ) => {
  const file = fs.readFileSync( path )

  return file.length === 0
}

const api = { isEmptyFileSync }
const asyncNames = 'isEmptyFile'

const fs = MemoryFS( {}, { api, asyncNames } )

fs.writeFileSync( 'test.txt', 'abc' )
fs.writeFileSync( 'empty.txt', '' )

fs.isEmptyFileSync( 'test.txt' ) // false
fs.isEmptyFileSync( 'empty.txt' ) // true

fs.isEmptyFile( 'empty.txt', ( err, result ) => {
  if( err ) return console.error( err )

  console.log( result )
})

If you want to patch existing methods, require the existing api.js from the src folder, get the method(s) you want, and write a wrapper method that can call the original:

const MemoryFS = require( '@mojule/memory-fs' )
const existing = require( '@mojule/memory-fs/src/api' )

const log = [ 'writeFile', 'mkdir' ]

const api = {}

log.forEach( name => {
  api[ name ] = ( ...args ) => {
    console.log( ...args )

    return existing[ name ]( ...args )
  }
})

// writeFile and mkdir should now log their args out when called
const fs = MemoryFS( {}, { api } )

Changes from webpack/memory-fs

MemoryFS is a factory function rather than a class constructor, so that the resultant fs methods can be promisified without having to call .bind. It should be completely backwards compatible aside from you have to drop the new when instantiating it, and some utility functions being moved (below)
Cleaned up conversion of sync -> async functions
Extracted repeated code throughout wherever it was traversing the data with a path out to a single function to make it easier to maintain and allow a possible refactor in future to use different backing stores
Moved normalize, join and pathToArray utility functions from fs instance to MemoryFS - eg MemoryFS.normalize( ... ) etc.
Made the API patchable via options