In javascript, how to trigger event when a variable's value is changed? [duplicate]

Answer 1

If you were willing to have about a 1 millisecond delay between checks, you could place

window.setInterval()

on it, for example this won't crash your browser:

window.setInterval(function() {
    if (trafficLightIsGreen && !someoneIsRunningTheLight) {
        go();
    }
}, 1);