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Piping readable data into writable streams

From: Node.js Essential Training

Video: Piping readable data into writable streams

In some cases, you don't necessarily want to directly handle the data coming from a stream. You just want to send it somewhere else. This is possible using a pipe. In this video, we'll pipe incoming data into another stream. Let's go to the exercise files. Go to chapter nine, video four, and then copy the files to the desktop. Now let's have a look at pipe.js. On line one, we're requiring the file system module. Then on lines three and four you'll notice we're creating a read stream and a write stream.

Piping readable data into writable streams

In some cases, you don't necessarily want to directly handle the data coming from a stream. You just want to send it somewhere else. This is possible using a pipe. In this video, we'll pipe incoming data into another stream. Let's go to the exercise files. Go to chapter nine, video four, and then copy the files to the desktop. Now let's have a look at pipe.js. On line one, we're requiring the file system module. Then on lines three and four you'll notice we're creating a read stream and a write stream.

We're going to pipe all of the data from the readable stream into the writable stream. This is going to create a copy of the data. Now, next there are two calls to stream.pipe. The first one is sending all the data to process.stdout. This is going to output all of the contents on the terminal screen. Now, the second one pipes the data to the writable stream we just created. This is going to copy all the data from the readable stream to the file on the other end of the writable stream.

Again, these streams are not holding all the data in memory. Its being handled in chunks behind the scenes, even though we aren't handling them directly here. So lets run the file now. Go to terminal and change directory to the desktop, that's with a capital D. And now type node and pipe.js. All of the data made it onto the screen, and now we have a copy.json file. This copy.json file is the exact same as the data.json file. To show that that's the case, I'm going to use the dif command.

Dif is going to show us all the changes, if any, between the two files. So I'm going to type dif, space, and then data.json. And then another space and then copy.json. And then I'm going to press return. So there is no difference between those two files. Readable streams can be piped into writable streams. This can simplify data processing if you just need to move data from one place to another. In the next video we will work with streams that are both readable and writable.

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This video is part of

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Node.js Essential Training

52 video lessons · 11732 viewers

Joseph LeBlanc
Author

 
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  1. 3m 9s
    1. Welcome
      42s
    2. What you should know before watching this course
      57s
    3. Using the exercise files
      47s
    4. Using the challenges
      43s
  2. 18m 50s
    1. Why use Node.js?
      2m 1s
    2. Choosing a Node.js installation process
      4m 56s
    3. Installing Node.js on the Mac
      2m 5s
    4. Installing Node.js on Windows
      1m 43s
    5. Installing Node.js via Node Version Manager on Ubuntu Linux
      4m 45s
    6. Installing Node.js via Node Version Manager on a Mac
      3m 20s
  3. 13m 54s
    1. Exploring language additions to the V8 JavaScript engine
      3m 38s
    2. Understanding require() and modules
      6m 39s
    3. Understanding callback execution in the event loop
      3m 37s
  4. 12m 23s
    1. Initializing Node.js projects
      2m 37s
    2. Finding an NPM
      3m 30s
    3. Maintaining projects using the npm command
      6m 16s
  5. 21m 4s
    1. Creating modules with getters and setters
      6m 33s
    2. Understanding module caching and scopes
      6m 15s
    3. Implementing JavaScript creational patterns
      5m 8s
    4. Challenge: Leveraging module caching
      55s
    5. Solution: Leveraging module caching
      2m 13s
  6. 32m 27s
    1. Starting Express applications
      3m 42s
    2. Handling GET requests returning JSON
      3m 26s
    3. Navigating large datasets using request variables in routes
      5m 4s
    4. Modifying data through PUT requests
      4m 32s
    5. Supplying middleware to modify HTTP response headers
      4m 37s
    6. Generating HTML views in Jade
      8m 9s
    7. Challenge: List all records as JSON
      37s
    8. Solution: List all records as JSON
      2m 20s
  7. 25m 37s
    1. Evaluating unit testing methodologies
      3m 8s
    2. Isolating existing code for testing
      6m 47s
    3. Supplying helpers for test data
      2m 35s
    4. Writing unit tests with Mocha
      6m 5s
    5. Simulating HTTP requests with SuperTest
      7m 2s
  8. 28m 45s
    1. Connecting to MongoDB via Mongoose
      4m 16s
    2. Defining schemas for collections in Mongoose
      3m 47s
    3. Querying MongoDB collections
      5m 32s
    4. Persisting Express sessions through MongoDB and mongo-connect
      7m 6s
    5. Logging in to Express applications using Passport
      8m 4s
  9. 21m 47s
    1. Controlling the built-in REPL
      4m 18s
    2. Constructing a custom REPL
      5m 40s
    3. Receiving command-line arguments with Optimist
      6m 14s
    4. Building command-line tools
      3m 35s
    5. Challenge: Launch a custom REPL from a command
      41s
    6. Solution: Launch a custom REPL from a command
      1m 19s
  10. 15m 46s
    1. Emitting events and attaching listeners
      5m 32s
    2. Streaming chunked data through readable streams
      2m 33s
    3. Controlling readable streams
      1m 52s
    4. Piping readable data into writable streams
      2m 10s
    5. Handling duplex streams over TCP
      3m 39s
  11. 4m 6s
    1. Deploying projects to cloud hosting services
      2m 36s
    2. Finding Node.js resources
      1m 30s

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