--- /dev/null
+var global = require('../internals/global');
+var getOwnPropertyDescriptor = require('../internals/object-get-own-property-descriptor').f;
+var macrotask = require('../internals/task').set;
+var IS_IOS = require('../internals/engine-is-ios');
+var IS_WEBOS_WEBKIT = require('../internals/engine-is-webos-webkit');
+var IS_NODE = require('../internals/engine-is-node');
+
+var MutationObserver = global.MutationObserver || global.WebKitMutationObserver;
+var document = global.document;
+var process = global.process;
+var Promise = global.Promise;
+// Node.js 11 shows ExperimentalWarning on getting `queueMicrotask`
+var queueMicrotaskDescriptor = getOwnPropertyDescriptor(global, 'queueMicrotask');
+var queueMicrotask = queueMicrotaskDescriptor && queueMicrotaskDescriptor.value;
+
+var flush, head, last, notify, toggle, node, promise, then;
+
+// modern engines have queueMicrotask method
+if (!queueMicrotask) {
+ flush = function () {
+ var parent, fn;
+ if (IS_NODE && (parent = process.domain)) parent.exit();
+ while (head) {
+ fn = head.fn;
+ head = head.next;
+ try {
+ fn();
+ } catch (error) {
+ if (head) notify();
+ else last = undefined;
+ throw error;
+ }
+ } last = undefined;
+ if (parent) parent.enter();
+ };
+
+ // browsers with MutationObserver, except iOS - https://github.com/zloirock/core-js/issues/339
+ // also except WebOS Webkit https://github.com/zloirock/core-js/issues/898
+ if (!IS_IOS && !IS_NODE && !IS_WEBOS_WEBKIT && MutationObserver && document) {
+ toggle = true;
+ node = document.createTextNode('');
+ new MutationObserver(flush).observe(node, { characterData: true });
+ notify = function () {
+ node.data = toggle = !toggle;
+ };
+ // environments with maybe non-completely correct, but existent Promise
+ } else if (Promise && Promise.resolve) {
+ // Promise.resolve without an argument throws an error in LG WebOS 2
+ promise = Promise.resolve(undefined);
+ then = promise.then;
+ notify = function () {
+ then.call(promise, flush);
+ };
+ // Node.js without promises
+ } else if (IS_NODE) {
+ notify = function () {
+ process.nextTick(flush);
+ };
+ // for other environments - macrotask based on:
+ // - setImmediate
+ // - MessageChannel
+ // - window.postMessag
+ // - onreadystatechange
+ // - setTimeout
+ } else {
+ notify = function () {
+ // strange IE + webpack dev server bug - use .call(global)
+ macrotask.call(global, flush);
+ };
+ }
+}
+
+module.exports = queueMicrotask || function (fn) {
+ var task = { fn: fn, next: undefined };
+ if (last) last.next = task;
+ if (!head) {
+ head = task;
+ notify();
+ } last = task;
+};