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

Answer 1

function should_i_go_now() {
    if(trafficLightIsGreen && !someoneIsRunningTheLight) {
        go();
    } else {
        setTimeout(function(){
            should_i_go_now();
        },30);
    }
}
setTimeout(function(){
    should_i_go_now();
},30);