1var stream = require('stream') 2 3 4function isStream (obj) { 5 return obj instanceof stream.Stream 6} 7 8 9function isReadable (obj) { 10 return isStream(obj) && typeof obj._read == 'function' && typeof obj._readableState == 'object' 11} 12 13 14function isWritable (obj) { 15 return isStream(obj) && typeof obj._write == 'function' && typeof obj._writableState == 'object' 16} 17 18 19function isDuplex (obj) { 20 return isReadable(obj) && isWritable(obj) 21} 22 23 24module.exports = isStream 25module.exports.isReadable = isReadable 26module.exports.isWritable = isWritable 27module.exports.isDuplex = isDuplex 28