Javascript regex for matching/extracting file extension

Question

The following regex

var patt1=/[0-9a-z]+$/i;

extracts the file extension of strings such as

filename-jpg
filename#gif
fil         


        

Answer 1

ONELINER:

let ext = (filename.match(/\.([^.]*?)(?=\?|#|$)/) || [])[1] 

above solution include links. It takes everything between last dot and first "?" or "#" char or string end. To ignore "?" and "#" characters use /\.([^.]*)$/. To ignore only "#" use /\.([^.]*?)(?=\?|$)/. Examples

function getExtension(filename) {
  return (filename.match(/\.([^.]*?)(?=\?|#|$)/) || [])[1];
}


// TEST
[
  "abcd.Ef1",
  "abcd.efg",
  "abcd.efg?aaa&a?a=b#cb",
  "abcd.efg#aaa__aa?bb",
  "abcd",
  "abcdefg?aaa&aa=bb",
  "abcdefg#aaa__bb",
].forEach(t=> console.log(`${t.padEnd(21,' ')} -> ${getExtension(t)}`))