browserify-adventure/problems/writing_transforms/solution.txt

learn browserify with this educational adventure

Here is the reference solution for the more adventurous option:

  var through = require('through2');
  var split = require('split');
  var sprintf = require('sprintf');
  var quote = require('quote-stream');
  var combiner = require('stream-combiner');
  
  module.exports = function (file) {
      if (!/\.txt$/.test(file)) return through();
      var num = 0;
      var liner = through(function write (buf, enc, next) {
          var line = buf.toString('utf8') + '\n';
          if (num % 5 === 0) {
              this.push(sprintf('%3d %s', num, line));
          }
          else this.push('    ' + line);
          num ++;
          next();
      });
      var prefix = through();
      prefix.write('module.exports=');
      return combiner(split(), liner, quote(), prefix);
  };

In this solution, for `.txt` files, we set up a pipeline with
`stream-combiner`. The source contents are split up line-by-line with the
`split` module, then our `liner` transform adds padded line numbers every
5th line. We quote the result using `quote-stream` and add a
`module.exports=` prefix to the entire result.

You could've also just repurposed your solution to "using transforms" with
concat-stream here too.