inventory.js

function inventory(input) {
    let index = 0;
    let itemList = input[index].split(`, `);
    index++;
    let commandLine = input[index];
    index++;

    while (commandLine !== "Craft!") {
        let commands = commandLine.split(` - `);
        let command = commands[0];
        let item;
        let item2;
        if (commands[1].includes(`:`)) {
            let combineList = commands[1].split(`:`);
            item = combineList[0];
            item2 = combineList[1];
        } else {
            item = commands[1];
        }

        if (!itemList.includes(item) && command === "Collect") {
            itemList.push(item);
        }

        if (itemList.includes(item)) {
            let itemIndex = itemList.indexOf(item);
            switch (command) {
                case "Drop":
                    itemList.splice(itemIndex, 1);
                    break;
                case "Combine Items":
                    itemList.splice(++itemIndex, 0, item2);
                    break;
                case "Renew":
                    itemList.splice(itemIndex, 1);
                    itemList.push(item);
                    break;
            }
        }
        commandLine = input[index];
        index++;
    }
    console.log(itemList.join(`, `));
}

inventory([
    'Iron, Wood, Sword',
    'Collect - Gold',
    'Drop - Wood',
    'Craft!'
]);
inventory([
    'Iron, Sword',
    'Drop - Bronze',
    'Combine Items - Sword:Bow',
    'Renew - Iron',
    'Craft!'
]);