House party

function solve(arr) {
    let newArr = [];

    for (let element of arr) {
        let command = element.split(' ');
        let name = command[0];
        if (command.length === 3) {
            if (newArr.includes(name)) {
                console.log(`${name} is already in the list!`);
            } else{
                newArr.push(name);
            }
        } else if (command.length === 4) {
            if (newArr.includes(name)) {
                newArr.filter(names => names !== name);
            } else{
                console.log(`${name} is not in the list!`);
            }
        }
    }

    return newArr.join(`\n`)
}

console.log(solve(['Allie is going!', 'George is going!', 'John is not going!', 'George is not going!']));