The Pianist JS Fundamentals

function thePianist(arr) {
    let piecesNumber = arr.shift();
    let pieceName = '';
    let composer = '';
    let key = '';
    let pieces = {};

    for (let line = 0; line < piecesNumber; line++) {
        let pieceInfo = arr.shift().split('|');
        pieceName = pieceInfo[0];
        composer = pieceInfo[1];
        key = pieceInfo[2];
        pieces[pieceName] = { composer: composer, key: key };
    }
    for (let line of arr) {
        let tokens = line.split('|');
        let command = tokens[0];
        let pieceName = tokens[1];
        let composer = tokens[2];
        let key = tokens[3];

        if (command === "Add") {
            if (pieces.hasOwnProperty(pieceName)) {
                console.log(`${pieceName} is already in the collection!`);
            } else {
                pieces[pieceName] = { composer: composer, key: key }
                console.log(` ${pieceName} by ${composer} in ${key} added to the collection!`);
            }
        } else if (command === "Remove") {
            if (pieces.hasOwnProperty(pieceName)) {
                delete pieces[pieceName];
                console.log(`Successfully removed ${pieceName}!`);
            } else {
                console.log(`Invalid operation! ${pieceName} does not exist in the collection.`);
            }
        } else if (command === "ChangeKey") {
            if (pieces.hasOwnProperty(pieceName)) {
                let newKey = tokens[2];
                pieces[pieceName].key = newKey;
                console.log(`Changed the key of ${pieceName} to ${newKey}!`);
            } else {
                console.log(`Invalid operation! ${pieceName} does not exist in the collection.`);
            }
        } else if (command === "Stop") {
            for (let pieceName in pieces) {
                let composer = pieces[pieceName].composer;
                let key = pieces[pieceName].key;
                console.log(`${pieceName} -> Composer: ${composer}, Key: ${key}`);
            }
        }
    }
}