text: var ctx                = require('./_ctx')
    , invoke             = require('./_invoke')
    , html               = require('./_html')
    , cel                = require('./_dom-create')
    , global             = require('./_global')
    , process            = global.process
    , setTask            = global.setImmediate
    , clearTask          = global.clearImmediate
    , MessageChannel     = global.MessageChannel
    , counter            = 0
    , queue              = {}
    , ONREADYSTATECHANGE = 'onreadystatechange'
    , defer, channel, port;
  var run = function(){
    var id = +this;
    if(queue.hasOwnProperty(id)){
      var fn = queue[id];
      delete queue[id];
      fn();
    }
  };
  var listener = function(event){
    run.call(event.data);
  };
  // Node.js 0.9+ & IE10+ has setImmediate, otherwise:
  if(!setTask || !clearTask){
    setTask = function setImmediate(fn){
      var args = [], i = 1;
      while(arguments.length > i)args.push(arguments[i++]);
      queue[++counter] = function(){
        invoke(typeof fn == 'function' ? fn : Function(fn), args);
      };
      defer(counter);
      return counter;
    };
    clearTask = function clearImmediate(id){
      delete queue[id];
    };
    // Node.js 0.8-
    if(require('./_cof')(process) == 'process'){
      defer = function(id){
        process.nextTick(ctx(run, id, 1));
      };
    // Browsers with MessageChannel, includes WebWorkers
    } else if(MessageChannel){
      channel = new MessageChannel;
      port    = channel.port2;
      channel.port1.onmessage = listener;
      defer = ctx(port.postMessage, port, 1);
    // Browsers with postMessage, skip WebWorkers
    // IE8 has postMessage, but it's sync & typeof its postMessage is 'object'
    } else if(global.addEventListener && typeof postMessage == 'function' && !global.importScripts){
      defer = function(id){
        global.postMessage(id + '', '*');
      };
      global.addEventListener('message', listener, false);
    // IE8-
    } else if(ONREADYSTATECHANGE in cel('script')){
      defer = function(id){
        html.appendChild(cel('script'))[ONREADYSTATECHANGE] = function(){
          html.removeChild(this);
          run.call(id);
        };
      };
    // Rest old browsers
    } else {
      defer = function(id){
        setTimeout(ctx(run, id, 1), 0);
      };
    }
  }
  module.exports = {
    set:   setTask,
    clear: clearTask
  };