var len = 0;

export default function asap(callback, arg) {

queue[len] = callback;
queue[len + 1] = arg;
len += 2;
if (len === 2) {
  // If len is 1, that means that we need to schedule an async flush.
  // If additional callbacks are queued before the queue is flushed, they
  // will be processed by this flush that we are scheduling.
  scheduleFlush();
}

}

var browserGlobal = (typeof window !== 'undefined') ? window : {}; var BrowserMutationObserver = browserGlobal.MutationObserver || browserGlobal.WebKitMutationObserver;

// test for web worker but not in IE10 var isWorker = typeof Uint8ClampedArray !== 'undefined' &&

typeof importScripts !== 'undefined' &&
typeof MessageChannel !== 'undefined';

// node function useNextTick() {

return function() {
  process.nextTick(flush);
};

}

function useMutationObserver() {

var iterations = 0;
var observer = new BrowserMutationObserver(flush);
var node = document.createTextNode('');
observer.observe(node, { characterData: true });

return function() {
  node.data = (iterations = ++iterations % 2);
};

}

// web worker function useMessageChannel() {

var channel = new MessageChannel();
channel.port1.onmessage = flush;
return function () {
  channel.port2.postMessage(0);
};

}

function useSetTimeout() {

return function() {
  setTimeout(flush, 1);
};

}

var queue = new Array(1000); function flush() {

for (var i = 0; i < len; i+=2) {
  var callback = queue[i];
  var arg = queue[i+1];

  callback(arg);

  queue[i] = undefined;
  queue[i+1] = undefined;
}

len = 0;

}

var scheduleFlush;

// Decide what async method to use to triggering processing of queued callbacks: if (typeof process !== 'undefined' && {}.toString.call(process) === '[object process]') {

scheduleFlush = useNextTick();

} else if (BrowserMutationObserver) {

scheduleFlush = useMutationObserver();

} else if (isWorker) {

scheduleFlush = useMessageChannel();

} else {

scheduleFlush = useSetTimeout();

}