text: function igraber (arr, pattern, value) {
    if (!value) {
      return arr.map( function (each, index) {
        if (each === pattern) return index
      }).filter( function (each) {
        if (each) return each
      })
    }
    if (value) {
      return arr.filter( function (each) {
        if (each === pattern)
        return each
      })
    }
  }
  
  function igrp (arr, pattern, value, callback) {
    if (Array.isArray(arr) !== true) throw new TypeError('1st argument should be array.')
    callback(null, igraber(arr, pattern, value))
  }
  
  module.exports = igrp
  