SOURCE

var w1Date, w2Date;
function w1() {
    w1Date = Date.now()
}
function w2() {
    w2Date = Date.now()
    console.log(' time.sp: ', w2Date - w1Date, ' ms')
}

setTimeout(w1, 100)
setTimeout(w2, 500)
function timeLoop(k) {
    var now = Date.now()
    while (Date.now() - now < k) { 
        // console.log(k)
    }
}
timeLoop(500)