//案例1
var str = '<img src="https://img.edows.cn/2020-01-01/order/101/cut/77bdefbc-6800-409f-925a-fb9ac2599068.jpg" alt="">';
//截取以https开头.jpg结尾的内容
var rep = /https.*?\.jpg/gi;
console.log(str.match(rep));
//案例2
//截取所有img标签
var reg2 = /(.*?)<img.+?alt=('|")(.*?)\2.*?>([^<]*)/gi;
var str2 = "你好<img src='aaa.gif' alt='图1'>天气不错<img src='bbb.gif' alt='图2'>哈哈";
console.log(str2.match(reg2));