Parallel execution of functions

gistfile1.js

/**
 * Calls the functions passed in `funcs` taking callbacks in parallel, calling
 * the callback passed to `doParallel` after each of the other functions have
 * finished.  The `callback` parameter is only called once.
 */
function doParallel(funcs, callback) {
  var maxCount = funcs.length
    , count    = 0

  function f() {
    count++;
    if (count == maxCount) { callback() }
  }

  if (maxCount == 0) { return callback() }

  funcs.forEach(function(fn) { fn(f) })
}

doParallel([
  function(cb) { /*...*/; cb() },
  function(cb) { /*...*/; cb() }
], function() {
  ...
})