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0.3.0 • Public • Published


Transforms data in a stream. Supports append, prepend, replace, erase, and compare


npm install @voliware/node-data-transform

Why do I need it?

If you have any stream in Node.js - a file, a TCP stream, a native Node request or response object - and you need to append data, prepend data, erase data, or replace data in the stream, you need this.

What is it?

A Transform object, which is a native Nodejs stream object. Transforms are passed to the pipe() function when dealing with readable streams. When data flows through the readable stream, it also flows through the transform. The transform can actually change the data as it goes down the pipe.

How do I use it?

Create one or many DataTransform objects that do as many of the following actions

  1. append(match, content)
  2. prepend(match, content)
  3. replace(match, content)
  4. erase(match)

Here, match means what are we looking for in the stream, and content is what we will append, prepend, or replace it with.


In this example, we will create just one DataTransform that will erase data, append some data with a file, prepend some data with a file, and replace some data with text. Note that the matches are named the same as the functions for clarity.

Input HTML file

    <!-- append -->
    <!-- prepend -->
    <!-- replace -->
    <!-- erase -->


let readable = Fs.createReadStream("base.html");
let writable = Fs.createWriteStream("index.html");
let datatransform = new DataTransform()
    .erase('<!-- erase -->')                     // erase <!-- erase --> 
    .append('<!-- append -->', "append.html")    // append with contents of a file
    .prepend('<!-- prepend -->', "prepend.html") // prepend with contents of a file
    .replace('<!-- replace -->', "Replaced!");   // replace with text

The result will be

    <!-- append --><div id="append"></div>
    <div id="prepend"></div><!-- prepend -->

What can I use it for?

A minifier

let datatransform = new DataTransform()
    .erase(' ')                                     // erase spaces
    .erase(Buffer.from([0x0d, 0x0a]))               // erase new lines 

An HTML injector

let datatransform = new DataTransform()
    .append('<!-- templates -->', "templates.html") // append with contents of a file

Search and replace in a file

let datatransform = new DataTransform()
    .replace('youre', 'you're)                      // search and replace 


There are two options when creating a DataTransform.

  1. concat
    • If true [default], all chunks are concatenated before processing. This is usually what you want.
    • If false, chunks are processed and sent downstream as they arrive.
  2. modifiers
    • Instead of using the API you can pass along an array of modifiers to the constructor.
    • Each modifier object has the properties of
      • action - "append", "prepend", "replace", or "erase"
      • match - the string or buffer to match against
      • content - the string or buffer to append, prepend, or replace with


let datatransform = new DataTransform({
    concat: false,
    modifiers: [
        {action: "append", match: "Joe", contents: " Senior"},
        {action: "prepend", match: "Joe", contents: "Mr. "},
        {action: "replace", match: "Joe", contents: "Matt"},
        {action: "erase", match: "bad words"}


npm i @voliware/node-data-transform

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