micro-toolkit/zmq-service-suite-broker-js

var RoundRobinStrategy = function(){

  // store key:index
  var state = { };

  this.clear = function(key) {
    return delete state[key];
  };

  this.next = function(key, elements) {

    if(!elements || elements.length === 0){
      return null;
    }

    var nextIndex = state[key] !== undefined ? ++state[key] : 0;

    // go to begging when next index greater than elements
    if(nextIndex >= elements.length){
      nextIndex = 0;
    }

    state[key] = nextIndex;

    return elements[nextIndex];
  };
};

module.exports = RoundRobinStrategy;