Alternative to setInterval / clearInterval

interval.js

var interval = (function() {
  var api = {};

  var idMap = {};
  var nextId = 0;

  api.set = function(task, ms) {
    var nextTime = Date.now() + ms;
    var id = nextId++;
  
    var trigger = function() {
      task();
      nextTime += ms;
      idMap[id] = setTimeout(trigger, nextTime - Date.now());
    };

    idMap[id] = setTimeout(trigger, nextTime - Date.now());

    return id;
  };

  api.clear = function(id) {
    clearTimeout(idMap[id]);
    delete idMap[id];
  };

  return api;
})();

var blockSync = function(ms) {
  var start = Date.now();
  while (Date.now() - start < ms);
};

var nativeDemo = function() {
  var start = Date.now();

  var id = setInterval(function() {
    console.log(((Date.now() - start) / 1000).toFixed(3));
    blockSync(500);
  }, 1000);

  setTimeout(function() {
    clearInterval(id);
  }, 10000);
};

var altDemo = function() {
  var start = Date.now();
  
  var id = interval.set(function() {
    console.log(((Date.now() - start) / 1000).toFixed(3));
    blockSync(500);
  }, 1000);

  setTimeout(function() {
    interval.clear(id);
  }, 10000);
};