utils for node fs

utils.js

// utitlies module
const path = require('path')
const fs = require('fs')

const noop = () => {}
const debug = process.env.DEBUG ? console.log : noop

// lang functions
const toString = Object.prototype.toString
const typeChecker = (expect) => (val) => toString.call(val) === `[object ${expect}]`
const isArr = typeChecker('Array')
const isObj = typeChecker('Object')
const isStr = typeChecker('String')
const isFn = typeChecker('Function')
const isNum = (val) => !isNaN(val) && typeChecker('Number')(val)
const isDate = typeChecker('Date')
const isUndef = typeChecker('Undefined')
const isNull = typeChecker('Null')
const isNil = val => (val === null || val === undefined)

function promisify(fn){
  return function(...args){
    return new Promise((resolve, reject) => {
      args.push((err, result) => {
        err ? reject(err) : resolve(result)
      })
      fn(...args)
    })
  }
}

// catch and supress errors for sync function calls
function supressify(fn, fallback = null){
  return (...args) => {
    try{
      return fn(...args)
    }catch(e){
      debug(e)
      return fallback
    }
  }
}

// json
const fromJson = json => {
  try{
    return JSON.parse(json)
  }catch(e){
    debug(e)
    return undefined
  }
}
const toJson = obj => {
  try{
    return JSON.stringify(obj)
  }catch(e){
    debug(e)
    return null
  }
}

// filesystem functions
const fileMode = (flag) => {
  flag = 'string' === typeof flag ? flag.trim().toLowerCase() : ''
  let mode = fs.constants.F_OK
  if(flag.indexOf('r') > -1){
    mode |= fs.constants.R_OK
  }
  if(flag.indexOf('w') > -1){
    mode |= fs.constants.W_OK
  }
  return mode
}

const access = promisify(fs.access)
const accessSync = supressify(fs.accessSync)
const readFile = promisify(fs.readFile)
const readFileSync = supressify(fs.readFileSync)
const writeFile = promisify(fs.writeFile)
const writeFileSync = supressify(fs.writeFileSync)
const unlink = promisify(fs.unlink)
const unlinkSync = supressify(fs.unlinkSync)

const checkFile = (file, expect = '') => access(file, fileMode(expect)).then(() => true, () => false)
const checkFileSync = (file, expect = '') => isUndef(accessSync(file, fileMode(expect)))

const mkdirSync = (dir) => {
  try{
    if(isUndef(accessSync(dir))){
      return -1
    }
    fs.mkdirSync(dir, {recursive: true, mode: 0o755})
    return 1
  }catch(e){
    debug(e)
    return 0
  }
}
const mkdir = (dir) => Promise.resolve(mkdirSync(dir))

const readJson = (file) => readFile(file, 'utf-8').then(fromJson)
const readJsonSync = (file) => fromJson(readFileSync(file, 'utf-8'))

const writeJson = (file, data) => {
  const json = toJson(data)
  if(isNull(json)){
    return Promise.reject('fail to serialize data to JSON')
  }
  return writeFile(file, json, 'utf-8')
}
const writeJsonSync = (file, data) => {
  const json = toJson(data)
  if(isNull(json)){
    return false
  }
  return isUndef(writeFileSync(file, json, 'utf-8'))
}

module.exports = {
  noop, debug,
  isArr, isObj, isStr, isFn, isNum, isDate, isUndef, isNull, isNil,
  access, accessSync,
  readFile, readFileSync,
  writeFile, writeFileSync,
  checkFile, checkFileSync,
  mkdir, mkdirSync,
  unlink, unlinkSync,
  readJson, readJsonSync,
  writeJson, writeJsonSync
}