Getting started with streams

In the previous section, we learned why streams are so powerful, but also that they are everywhere in Node.js, starting from its core modules. For example, we have seen that the fs module has createReadStream() for reading from a file and createWriteStream() for writing to a file, the HTTP request and response objects are essentially streams, the zlib module allows us to compress and decompress data using a streaming interface and, finally, even the crypto module exposes some useful streaming primitives like createCipheriv and createDecipheriv.

Now that we know why streams are so important, let's take a step back and start to explore them in more detail.

Anatomy of streams

Every stream in Node.js is an implementation of one of the four base abstract classes available in the stream core module:

• Readable
• Writable
• Duplex
• Transform

Each stream class is also an instance of EventEmitter. Streams, in...