Extract number between brackets and increment

JavaScript

existingId = 'fisher[27].man';
newIdOnly= existingId .replace(/fisher\[(\d+)\].man+/g,"$1");
console.log(newIdOnly);

newId = existingId .replace(/(\d+)+/g, function(match, number) {
       return parseInt(number)+1;
});
console.log(newId);