[Javascript] Regex: '$`', '$&', '$''

var input = "foobar";
var result = input.replace('bar', '$`'); // $`: replace 'bar'  with everything before our match.--> foofoo

var input = "foobarbaz";
var result = input.replace('bar', '$&'); // $&: the match one --> foobarbaz

var input = "foobarbaz";
var result = input.replace('bar', '$\''); // $': replace with everything come after the match --> foobazbaz

var input = "foobarbaz";
var result = input.replace('bar', '$$'); // repalce with $ --> foo$baz

var input = "foobarbaz";
var result = input.replace('bar', '?'); // replace with ? --> foo?baz

console.log(result);