//程序目的，去掉圖片路徑中的域名
var str = '<img src="http://www.49028c.com/images/logo.gif">';
var reg1 = /(/<img)(.*(?=(http|https)/:////))((http|https)/:////[^//]*)/gim;
str.match(reg1);
alert(str.replace(RegExp.$4,'');

var str = '<img src="http://www.49028c.com/images/logo.gif">武林網首頁的<a href="http://www.49028c.com">鏈接</a>';

//與貪婪匹配的差別就是多了一個問號“?”，貪婪".*",非貪婪".*?"
var reg1 = /(/<img)(.*?(?=(http|https)/:////))((http|https)/:////[^//]*)/gim;