funstream/is.js

Funstream gives you iteratorish methods on your streams.

'use strict'
const isaStream = require('isa-stream')

exports.scalar = isScalar
exports.iterator = isIterator
exports.asyncIterator = isAsyncIterator
exports.thenable = isThenable
exports.plainObject = isPlainObject
exports.Readable = isaStream.Readable
exports.Writable = isaStream.Writable
exports.Duplex = isaStream.Duplex

function isScalar (value) {
  if (value == null) return true
  if (Buffer.isBuffer(value)) return true
  switch (typeof value) {
    case 'string':
    case 'number':
    case 'bigint':
    case 'boolean':
    case 'symbol':
      return true
    default:
      return false
  }
}

function isIterator (value) {
  try {
    return Symbol.iterator in value && 'next' in value
  } catch (_) {
    return false
  }
}

function isAsyncIterator (value) {
  try {
    return Symbol.asyncIterator in value && 'next' in value
  } catch (_) {
    return false
  }
}

function isThenable (value) {
  try {
    return 'then' in value
  } catch (_) {
    return false
  }
}

function isPlainObject (value) {
  if (value == null) return false
  if (typeof value !== 'object') return false
  if (Array.isArray(value)) return false
  if (Buffer.isBuffer(value)) return false
  if (isIterator(value)) return false
  if (isAsyncIterator(value)) return false
  if (isaStream.Readable(value)) return false
  if (isaStream.Writable(value)) return false
  if (isThenable(value)) return false
  return true
}