前向匹配(?=)
var str = 'abcabcad';
var re = /a(?=d)/g; //只匹配a后面接d的a
str = str.replace(re,'*');
//"abcabc*d"
var str = 'abcabcad';
var re = /a(?=bc)/g; //只匹配a后面接bc的a
str = str.replace(re,'*');
//"*bc*bcad"
捕获分组
var str="cccabbammmm";
var re = /(\w)(\w)\2\1/g;
str = str.replace(re,"*") //会匹配str里的abba和mmmm,因为他们都符合这种结构
//"ccc**"
$1-9的理解,(这里仍然不全,有待后续的研究)
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/n