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var global = require('../internals/global');
var bind = require('../internals/function-bind-context');
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_IOS_PEBBLE = require('../internals/engine-is-ios-pebble');
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 (!IS_IOS_PEBBLE && Promise && Promise.resolve) {
// Promise.resolve without an argument throws an error in LG WebOS 2
promise = Promise.resolve(undefined);
// workaround of WebKit ~ iOS Safari 10.1 bug
promise.constructor = Promise;
then = bind(promise.then, promise);
notify = function () {
then(flush);
};
// Node.js without promises
} else if (IS_NODE) {
notify = function () {
process.nextTick(flush);
};
// for other environments - macrotask based on:
// - setImmediate
// - MessageChannel
// - window.postMessage
// - onreadystatechange
// - setTimeout
} else {
// strange IE + webpack dev server bug - use .bind(global)
macrotask = bind(macrotask, global);
notify = function () {
macrotask(flush);
};
}
}
module.exports = queueMicrotask || function (fn) {
var task = { fn: fn, next: undefined };
if (last) last.next = task;
if (!head) {
head = task;
notify();
} last = task;
};