illegal use of break statement; javascript

break is to break out of a loop like for, while, switch etc which you don't have here, you need to use return to break the execution flow of the current function and return to the caller.

function loop() {
    if (isPlaying) {
        jet1.draw();
        drawAllEnemies();
        requestAnimFrame(loop);
        if (game == 1) {
           return
        }
    }
}

Note: This does not cover the logic behind the if condition or when to return from the method, for that we need to have more context regarding the drawAllEnemies and requestAnimFrame method as well as how game value is updated

You need to make sure requestAnimFrame stops being called once game == 1. A break statement only exits a traditional loop (e.g. while()).

function loop() {
    if (isPlaying) {
        jet1.draw();
        drawAllEnemies();
        if (game != 1) {
            requestAnimFrame(loop);
        }
    }
}

Or alternatively you could simply skip the second if condition and change the first condition to if (isPlaying && game !== 1). You would have to make a variable called game and give it a value of 0. Add 1 to it every game.