exec.js

const citiesStartingWithB = /B.*?\w+/g
const target = "Barcelona Viena Beijing Tokio Bogota";
let result;

while ((result = citiesStartingWithB.exec(target)) !== null) {
  console.log(`Match: ${result[0]}`);
  console.log(`Last Index at ${citiesStartingWithB.lastIndex}`);
}

// ✅ Output
// Match: Barcelona
// Last Index at 9
// Match: Beijing
// Last Index at 23
// Match: Bogota
// Last Index at 36