Question

I need to read a file line by line, and change a variable accordingly.
I would normally write this in PHP… but I decided to take the challenge.

I wrote:

fs = require('fs');
Lazy = require('lazy');
path = require('path');

files = fs.readdirSync('.');
var software = {};


files.forEach( function(fileName){


  var m; 
  if( m = fileName.match(/^(.*)\.txt$/) ){
    name = m[1];

    console.log("Processing file: " + fileName);
    software[name] = {};
    console.log("Software 1: %j",software);

    var section = 'unset';
    new Lazy(fs.createReadStream(fileName)).lines.forEach(
      function(line){
        var m;
        line = line + '';
        if( m = line.match(/^([a-zA-Z_]*):$/)){
          section = m[1];
          software[name][section] = '';
          console.log("Switching to section " + m[1]);
          console.log("Software 2: %j",software);
        } else if (line == '.'){
          section = 'unset'
        } else if (line == ''){
          section = 'unset'
        } else { 
          console.log("LINE: " + line) ;
          software[name][section] = software[name][section] + line + "\n";
          console.log("Software 3: %j",software);
        }
      }

    );   
  }

});

console.log("Software 4: %j",software);

Apart from the code being very ugly and very unoptimised, I am having trouble as when the last line prints, the “software” variable is not YET populated! I am guessing Lazy is asyncronous. So, it basically works, but “at some point later”. This is great, but… where do I write code when that important cycle, that fills in the software variable, is actually finished?!?

As requested: data to play with!

simply create “something.txt” and write:

name:
Name 1
.

Option 1:
Value 1
.

Option 2:
Value 2
.

Option 3:
Multi
Line
Value
.

Another_section:
Again
.

Merc.

Answer 1

The instances of Lazy returned by the library are EventEmitters, and it emits en event called pipe when a “set” of operations is complete:

new Lazy(
  ...
).on('pipe', function() {
  // all done
});

Modifying your code to use this event results in (the only change is near the bottom):

fs = require('fs');
Lazy = require('lazy');
path = require('path');

files = fs.readdirSync('.');
var software = {};


files.forEach( function(fileName){


  var m;
  if( m = fileName.match(/^(.*)\.txt$/) ){
    name = m[1];

    console.log("Processing file: " + fileName);
    software[name] = {};
    console.log("Software 1: %j",software);

    var section = 'unset';
    new Lazy(fs.createReadStream(fileName)).lines.forEach(
      function(line){
        var m;
        line = line + '';
        if( m = line.match(/^([a-zA-Z_]*):$/)){
          section = m[1];
          software[name][section] = '';
          console.log("Switching to section " + m[1]);
          console.log("Software 2: %j",software);
        } else if (line == '.'){
          section = 'unset'
        } else if (line == ''){
          section = 'unset'
        } else {
          console.log("LINE: " + line) ;
          software[name][section] = software[name][section] + line + "\n";
          console.log("Software 3: %j",software);
        }
      }

    ).on('pipe', function() {
      console.log("Software 4: %j",software);
    });
  }

});

[Edit] To answer your question regarding how I found this info:

I did indeed check out the source file for the project; I knew the library had a sum method that could be chained to instances of Lazy to sum up everything at the end; the code for that method calls foldr, and the code for that method listens for an event called pipeName, which is defaulted in line 22 as pipe.