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var global = require('./$.global')
, macrotask = require('./$.task').set
, Observer = global.MutationObserver || global.WebKitMutationObserver
, process = global.process
, Promise = global.Promise
, isNode = require('./$.cof')(process) == 'process'
, head, last, notify;
var flush = function(){
var parent, domain, fn;
if(isNode && (parent = process.domain)){
process.domain = null;
parent.exit();
}
while(head){
domain = head.domain;
fn = head.fn;
if(domain)domain.enter();
fn(); // <- currently we use it only for Promise - try / catch not required
if(domain)domain.exit();
head = head.next;
} last = undefined;
if(parent)parent.enter();
};
// Node.js
if(isNode){
notify = function(){
process.nextTick(flush);
};
// browsers with MutationObserver
} else if(Observer){
var toggle = 1
, node = document.createTextNode('');
new Observer(flush).observe(node, {characterData: true}); // eslint-disable-line no-new
notify = function(){
node.data = toggle = -toggle;
};
// environments with maybe non-completely correct, but existent Promise
} else if(Promise && Promise.resolve){
notify = function(){
Promise.resolve().then(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 = function asap(fn){
var task = {fn: fn, next: undefined, domain: isNode && process.domain};
if(last)last.next = task;
if(!head){
head = task;
notify();
} last = task;
};
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