Check FPS in JS? [closed]

Answer 1

In gameLoop, look at the difference between new Date and new Date from the last loop (store it in a variable).
In other words:

var lastLoop = new Date();
function gameLoop() { 
    var thisLoop = new Date();
    var fps = 1000 / (thisLoop - lastLoop);
    lastLoop = thisLoop;
    ...
}

thisLoop - lastLoop is the number of milliseconds that passed between the two loops.