正则表达式获取URL中的域名

正则：(http|https)://(www.)?(\w+(\.)?)+

测试1：https://www.amazon.co.uk/Wireless-iClever-Bluetooth-Backlight-Smartphone/dp/B018K5EJCQ/ref=sr_1_28?s=computers&ie=UTF8&qid=1496913940&sr=1-28&keywords=Bluetooth+Keyboard

结果1：https://www.amazon.co.uk

测试2：http://write./postedit?ref=toolbar&ticket=ST-82030-JMo9k3yzNotE0T270BVD-

结果2：http://write.

测试3：/s/blog_53edf7c10100ca09.html

结果3：