正则表达式：找出符号是否被等号包围

Question

I need a JS regex that will find matches of a word character that are not surrounded by any equal word characters. For example, if we are looking for b it should match aba or ubu and should not abc or bca .

Any characters in the given string are lowercase English letters, which are alternate (eg we can have ababa but cannot bbaa ).

I tried using lookarounds like this:

/b(?=a)/g

But I did not manage to figure out how do I replace the a so that we know that it is the same symbol that is on the left and the right side of b . Any insights are appreciated.

Answer 1

Using below regex:

(.)(b)(?=\1)

You are able to match these kind of characters. If you need to manipulate surrounded b s then you can code it like this:

> "aabb aba".replace(/(.)(b)(?=\1)/g, function(match, p1, p2) {
    return p1 + 'c';
});

< "aabb aca"

Answer 2

You might do as follows;

 var found = "abaubuiyiatbzsgegestsabn".match(/(\\w)[^\\1]\\1/g); console.log(found); 

Then if you would like to get all interlaced patterns such is in "abaubuiyiatbzsgegestsabn" you should not only get "geg" but also "ege"

 var str = "abaubuiyiatbzsgegestsabn".split(/(\\w)(?=[^\\1]\\1)/g) .slice(1) .reduce((p,c,i,a) => i&1 ? (p[p.length-1] += (a.slice(i) .join("") .slice(0,2)),p) : p.concat([[c]]) ,[]); console.log(str);