world tour - final exam - fundamentals

function world(input) {
    let tour = input.shift();
   // console.log(tour);
   let line = input.shift();
   while (line != "Travel") {
       let [command, firstArgument, secondArgument] = line.split(":");
       switch (command) {
           case "Add Stop":
               let index = Number(firstArgument);
               let str = secondArgument;
               if (index < tour.length && index >= 0) {
                    let split1 = tour.slice(0, index).concat(str);
                    let split2 = tour.slice(index, tour.length);
                    tour = split1 + split2;
               }
               console.log(tour);
               break;
            case "Remove Stop":
                let startIndex = Number(firstArgument);
                let endIndex = Number(secondArgument);
                if (startIndex < tour.length && startIndex >= 0
                    && endIndex < tour.length && endIndex >= 0) {
                    let split = tour.substring(startIndex, endIndex + 1);
                    tour = tour.replace(split, "");
                }
                console.log(tour);
                break;
           default:
               while (tour.includes(firstArgument) === true) {
                   tour = tour.replace(firstArgument, secondArgument);
               }
               console.log(tour);
               break;
       }
       line = input.shift();
   }
   console.log(`Ready for world tour! Planned stops: ${tour}`);
}

world(["Hawai::Cyprys-Greece",
"Add Stop:7:Rome",
"Remove Stop:11:16",
"Switch:Hawai:Bulgaria",
"Travel"]);