async_function.js

async.js

function async(i, callback) {
  timeout = Math.round(Math.random() * 3000);
  setTimeout(function() {
    console.log(i + ' is done');
    callback();
  }, timeout);
}

insert_step.js

var Step = require('step');

var collection = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

Step(

  function insertAll() {
    var self = this;
    collection.forEach(function(element) {
      async(element, self.parallel());
    });
  },
  function finalize(err) {
    if (err) { console.log(err);return;}
    console.log('done with no problem');
  }
);