browserify-adventure/problems/writing_transforms/problem.txt

learn browserify with this educational adventure

Building upon the previous "using transforms" section, write a custom
browserify transform so that in main.js you can simply do:

  var txt = require('./wake.txt');
  console.log(txt);

and the `txt` output will be formatted with the proper line-numbering as
from the previous level: printf("%3d %s", lineNum, line) every 5th line,
line numbers starting from zero and four leading spaces on the other
lines.

You'll first need to copy wake.txt to your local directory:

  cp $WAKE_FILE .

You will need to factor out your formatting code to be a node transform
stream, which you can learn more about in the stream-adventure nodeschool
workshop. The basic signature of a browserify transform is:

  var through = require('through2');
  
  module.exports = function (file) {
    if (!/\.txt$/.test(file)) return through();
    // ...
    return stream;
  };

where `stream` is a transform stream that will be written the original
source contents of `file` and should output the new transformed contents.

Transforms are run on all files in the current package that are loaded with
`require()`. For this problem we are only interested in transforming `.txt`
files, so we return a passthrough stream if the file extension is not
`.txt`.

The output of your stream will need to be valid javascript and will need to
interface with the module system, so your transform stream should generate
output that looks like:

  module.exports = "...transformed content goes here..."

You can either buffer up in the input with the `concat-stream` module and
run your previous solution to the previous "using transforms" level or if
you are feeling adventurous, you can string together `split2`,
`quote-stream`, and `through2` modules with `stream-combiner2` to build a
transform that processes the files in-place.

You will need to run browserify with `-t ./tr.js` where `tr.js` is the
filename of your transform. Copy the main.js from the beginning of this
problem description then to verify your solution, do:

  browserify -t ./tr.js main.js | $ADVENTURE_COMMAND verify

or to run your solution without verifying it do:

  browserify -t ./tr.js main.js | $ADVENTURE_COMMAND run