我个人对这个解决方案做了很多研究，我能找到的最好的解决方案实际上来自CloudFlare的“浏览器检查”:

function getHostname(){  
            secretDiv = document.createElement('div');
            secretDiv.innerHTML = "<a href='/'>x</a>";
            secretDiv = secretDiv.firstChild.href;
            var HasHTTPS = secretDiv.match(/https?:\/\//)[0];
            secretDiv = secretDiv.substr(HasHTTPS.length);
            secretDiv = secretDiv.substr(0, secretDiv.length - 1);
            return(secretDiv);  
}  

getHostname();

我重写了变量，使它更“人类”可读，但它比预期的工作做得更好。

import URL from 'url';

const pathname = URL.parse(url).path;
console.log(url.replace(pathname, ''));

这样就兼顾了协议。

代码:

var regex = /\w+.(com|co\.kr|be)/ig;
var urls = ['http://www.youtube.com/watch?v=ClkQA2Lb_iE',
            'http://youtu.be/ClkQA2Lb_iE',
            'http://www.example.com/12xy45',
            'http://example.com/random'];


$.each(urls, function(index, url) {
    var convertedUrl = url.match(regex);
    console.log(convertedUrl);
});

结果:

youtube.com
youtu.be
example.com
example.com

String.prototype.trim = function(){return his.replace(/^\s+|\s+$/g,"");}
function getHost(url){
    if("undefined"==typeof(url)||null==url) return "";
    url = url.trim(); if(""==url) return "";
    var _host,_arr;
    if(-1<url.indexOf("://")){
        _arr = url.split('://');
        if(-1<_arr[0].indexOf("/")||-1<_arr[0].indexOf(".")||-1<_arr[0].indexOf("\?")||-1<_arr[0].indexOf("\&")){
            _arr[0] = _arr[0].trim();
            if(0==_arr[0].indexOf("//")) _host = _arr[0].split("//")[1].split("/")[0].trim().split("\?")[0].split("\&")[0];
            else return "";
        }
        else{
            _arr[1] = _arr[1].trim();
            _host = _arr[1].split("/")[0].trim().split("\?")[0].split("\&")[0];
        }
    }
    else{
        if(0==url.indexOf("//")) _host = url.split("//")[1].split("/")[0].trim().split("\?")[0].split("\&")[0];
        else return "";
    }
    return _host;
}
function getHostname(url){
    if("undefined"==typeof(url)||null==url) return "";
    url = url.trim(); if(""==url) return "";
    return getHost(url).split(':')[0];
}
function getDomain(url){
    if("undefined"==typeof(url)||null==url) return "";
    url = url.trim(); if(""==url) return "";
    return getHostname(url).replace(/([a-zA-Z0-9]+.)/,"");
}

我尝试使用给定的解决方案，选择的解决方案对我的目的来说是多余的，而“创建一个元素”对我来说是一团糟。

它还没有准备好在URL的端口。我希望有人觉得它有用

function parseURL(url){
    parsed_url = {}

    if ( url == null || url.length == 0 )
        return parsed_url;

    protocol_i = url.indexOf('://');
    parsed_url.protocol = url.substr(0,protocol_i);

    remaining_url = url.substr(protocol_i + 3, url.length);
    domain_i = remaining_url.indexOf('/');
    domain_i = domain_i == -1 ? remaining_url.length - 1 : domain_i;
    parsed_url.domain = remaining_url.substr(0, domain_i);
    parsed_url.path = domain_i == -1 || domain_i + 1 == remaining_url.length ? null : remaining_url.substr(domain_i + 1, remaining_url.length);

    domain_parts = parsed_url.domain.split('.');
    switch ( domain_parts.length ){
        case 2:
          parsed_url.subdomain = null;
          parsed_url.host = domain_parts[0];
          parsed_url.tld = domain_parts[1];
          break;
        case 3:
          parsed_url.subdomain = domain_parts[0];
          parsed_url.host = domain_parts[1];
          parsed_url.tld = domain_parts[2];
          break;
        case 4:
          parsed_url.subdomain = domain_parts[0];
          parsed_url.host = domain_parts[1];
          parsed_url.tld = domain_parts[2] + '.' + domain_parts[3];
          break;
    }

    parsed_url.parent_domain = parsed_url.host + '.' + parsed_url.tld;

    return parsed_url;
}

运行:

parseURL('https://www.facebook.com/100003379429021_356001651189146');

结果:

Object {
    domain : "www.facebook.com",
    host : "facebook",
    path : "100003379429021_356001651189146",
    protocol : "https",
    subdomain : "www",
    tld : "com"
}

jquery Oneline

$('<a>').attr('href', document.location.href).prop('hostname');