Node.js - TriggerFlow

A simple library used to conditionally trigger methods.

Why?

Some patterns necessitate having triggers. For example, consider walking a directory tree:

walk('~/data')
.on('file', function(file) {
  //do some file processing
})
.end('end', function() {
  //move to another part of the program
})

What if when the end event is emitted, some file processing is still occurring? And let's say that the other part of your program needs this file processing to be completed, what do you do?

Install

npm install triggerflow

Usage

Revisiting the previous example, you can solve this problem quite easily with a trigger. A trigger can be thought of as a switch that fires a method when some conditions have been met. More specifically in the case of triggerflow, when the conditions meet a base condition.

In triggerflow, base conditions are when a boolean is true and when a number is 0.

Example:

var trigger = require('triggerflow');

var finishedTrigger = trigger({processing: 0, done: false}, function() { moveToNextPartOfProgram() })
  , processing = 0;

walk('~/data')
.on('file', function(file) {
  processing += 1;
  tf.update({processing: processing});
  processFile(file, function() { //hypothetical async file process function
    processing -= 1;
    tf.update({processing: processing});
  })
}).end('end', function() {
  tf.update({done: true});
})

The trigger is only fired and thus moveToNextPartOfProgram() is called when processing is 0 and done is true.

License

MIT Licensed

Copyright (c) 2012 JP Richardson