async.js

'use strict';

var collection = require('./collection');

//
// Pointless function that will replace callbacks once they are executed to
// prevent double execution from ever happening.
//
function noop() { /* you waste your time by reading this, see, I told you.. */ }

/**
 * Asynchronously iterate over the given data.
 *
 * @param {Mixed} data The data we need to iterate over
 * @param {Function} iterator Function that's called for each item.
 * @param {Function} fn The completion callback
 * @param {Object} options Async options.
 * @api public
 */
exports.each = function each(data, iterator, fn, options) {
  options = options || {};

  var size = collection.size(data)
    , completed = 0
    , timeout;

  if (!size) return fn();

  collection.each(data, function iterating(item) {
    iterator.call(options.context || iterator, item, function done(err) {
      if (err) {
        fn(err);
        return fn = noop;
      }

      if (++completed === size) {
        fn();
        if (timeout) clearTimeout(timeout);
        return fn = noop;
      }
    });
  });

  //
  // Optional timeout for when the operation takes to long.
  //
  if (options.timeout) timeout = setTimeout(function kill() {
    fn(new Error('Operation timed out'));
    fn = noop;
  }, options.timeout);
};