School Library kozmoza

function solve(input) {
    let bookShelves = input.shift().split("&");

      for (book of input) {
          let [currentCommand, currentBook, currentBook2] = book.split(" | ");

          if (currentCommand === 'Add Book') {
              if (!bookShelves.includes(currentBook)) {
                  bookShelves.unshift(currentBook);
              }
          } else if (currentCommand === 'Take Book') {
                bookShelves = bookShelves.filter(book => book !== currentBook);
          } else if (currentCommand ==='Insert Book') {
                bookShelves.push(currentBook);
          } else if (currentCommand === 'Check Book') {
              let index = Number(currentBook);
              if(bookShelves[index] !== undefined) {
                  console.log(bookShelves[index]);
              }
          } else if(currentCommand === 'Swap Books') {
              let [idx1, idx2] = [bookShelves.indexOf(currentBook), bookShelves.indexOf(currentBook2)];
              if(idx1 !== -1 && idx2 !== -1) {
                  [bookShelves[idx1], bookShelves[idx2]] = [currentBook2, currentBook];
              }
          } else if (currentCommand === 'Done') {
              console.log(bookShelves.join(', '));
              break;
          }
      }
  }