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Node.js - klaw

A Node.js file system walker extracted from fs-extra.

Install

npm i --save klaw

Name

klaw is walk backwards :p

Usage

klaw(directory, [options])

Returns a Readable stream that iterates through every file and directory starting with dir as the root. Every read() or data event returns an object with two properties: path and stats. path is the full path of the file and stats is an instance of fs.Stats.

directory: The directory to recursively walk. Type string.
options: Readable stream options and the following:
- queueMethod (string, default: 'shift'): Either 'shift' or 'pop'. On readdir() array, call either shift() or pop().
- pathSorter (function, default: undefined): Sorting function for Arrays.
- fs (object, default: require('fs')): Use this to hook into the fs methods or to use mock-fs
- filter (function, default: undefined): Filtering function for Arrays

Streams 1 (push) example:

var klaw = require('klaw')

var items = [] // files, directories, symlinks, etc
klaw('/some/dir')
  .on('data', function (item) {
    items.push(item.path)
  })
  .on('end', function () {
    console.dir(items) // => [ ... array of files]
  })

Streams 2 & 3 (pull) example:

var klaw = require('klaw')

var items = [] // files, directories, symlinks, etc
klaw('/some/dir')
  .on('readable', function () {
    var item
    while ((item = this.read())) {
      items.push(item.path)
    }
  })
  .on('end', function () {
    console.dir(items) // => [ ... array of files]
  })

If you're not sure of the differences on Node.js streams 1, 2, 3 then I'd recommend this resource as a good starting point: https://strongloop.com/strongblog/whats-new-io-js-beta-streams3/.

Error Handling

Listen for the error event.

Example:

var klaw = require('klaw')
klaw('/some/dir')
  .on('readable', function () {
    var item
    while ((item = this.read())) {
      // do something with the file
    }
  })
  .on('error', function (err, item) {
    console.log(err.message)
    console.log(item.path) // the file the error occurred on
  })
  .on('end', function () {
    console.dir(items) // => [ ... array of files]
  })

Aggregation / Filtering / Executing Actions (Through Streams)

On many occasions you may want to filter files based upon size, extension, etc. Or you may want to aggregate stats on certain file types. Or maybe you want to perform an action on certain file types.

You should use the module through2 to easily accomplish this.

Install through2:

npm i --save through2

Example (skipping directories):

var klaw = require('klaw')
var through2 = require('through2')

var excludeDirFilter = through2.obj(function (item, enc, next) {
  if (!item.stats.isDirectory()) this.push(item)
  next()
})

var items = [] // files, directories, symlinks, etc
klaw('/some/dir')
  .pipe(excludeDirFilter)
  .on('data', function (item) {
    items.push(item.path)
  })
  .on('end', function () {
    console.dir(items) // => [ ... array of files without directories]
  })

Example (ignore hidden directories):

var klaw = require('klaw')
var path = require('path')

var filterFunc = function(item){
  var basename = path.basename(item)
  return basename === '.' || basename[0] !== '.'
}

klaw('/some/dir', { filter : filterFunc  })
  .on('data', function(item){
    // only items of none hidden folders will reach here
  })

Example (totaling size of PNG files):

var klaw = require('klaw')
var path = require('path')
var through2 = require('through2')

var totalPngsInBytes = 0
var aggregatePngSize = through2.obj(function (item, enc, next) {
  if (path.extname(item.path) === '.png') {
    totalPngsInBytes += item.stats.size
  }
  this.push(item)
  next()
})

klaw('/some/dir')
  .pipe(aggregatePngSize)
  .on('data', function (item) {
    items.push(item.path)
  })
  .on('end', function () {
    console.dir(totalPngsInBytes) // => total of all pngs (bytes)
  })

Example (deleting all .tmp files):

var fs = require('fs')
var klaw = require('klaw')
var through2 = require('through2')

var deleteAction = through2.obj(function (item, enc, next) {
  this.push(item)

  if (path.extname(item.path) === '.tmp') {
    item.deleted = true
    fs.unklink(item.path, next)
  } else {
    item.deleted = false
    next()
  }  
})

var deletedFiles = []
klaw('/some/dir')
  .pipe(deleteAction)
  .on('data', function (item) {
    if (!item.deleted) return
    deletedFiles.push(item.path)
  })
  .on('end', function () {
    console.dir(deletedFiles) // => all deleted files
  })

You can even chain a bunch of these filters and aggregators together. By using multiple pipes.

Example (using multiple filters / aggregators):

klaw('/some/dir')
  .pipe(filterCertainFiles)
  .pipe(deleteSomeOtherFiles)
  .on('end', function () {
    console.log('all done!')
  })

Example passing (piping) through errors:

Node.js does not pipe() errors. This means that the error on one stream, like klaw will not pipe through to the next. If you want to do this, do the following:

var klaw = require('klaw')
var through2 = require('through2')

var excludeDirFilter = through2.obj(function (item, enc, next) {
  if (!item.stats.isDirectory()) this.push(item)
  next()
})

var items = [] // files, directories, symlinks, etc
klaw('/some/dir')
  .on('error', function (err) { excludeDirFilter.emit('error', err) }) // forward the error on
  .pipe(excludeDirFilter)
  .on('data', function (item) {
    items.push(item.path)
  })
  .on('end', function () {
    console.dir(items) // => [ ... array of files without directories]
  })

Searching Strategy

Pass in options for queueMethod and pathSorter to affect how the file system is recursively iterated. See the code for more details, it's less than 50 lines :)

License

MIT

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