A limited work-in-progress system with Pipeworks.

wip.js

var pipeworks = require('pipeworks');

var wip = 0;
var limit = 2;
var total = 0;

var check = function(context, next) {
  if (wip === limit) {
    console.log('I\'ll eat', context.food, 'later...');
    setTimeout(check.bind(this, context, next), 2000);
  } else {
    next(context);
  }
};

var mealtime = pipeworks()
  .fit(check)
  .fit(function(context, next) {
    wip++;
    next(context);
  })
  .fit(function(context, next) {
    setTimeout(function() {
      console.log('I eat', context.food);
      next(context);
    }, 100);
  })
  .fit(function(context, next) {
    wip--;
    next(context);
  })
  .fit(function(context, next) {
    total++;
    if (total < foods.length) {
      console.log('I\'m still hungry...');
    } else {
      console.log('Now I`m stuffed!');
    }

    next(context);
  });

var foods = ['burritos', 'tacos', 'nachos', 'enchiladas'];

foods.forEach(function(food) {
  mealtime.flow({ food: food });
});

/* Output:
I'll eat nachos later...
I'll eat enchiladas later...
I eat burritos
I'm still hungry...
I eat tacos
I'm still hungry...
<...pause...>
I eat nachos
I'm still hungry...
I eat enchiladas
Now I`m stuffed!
*/