【Javascript】時間の計測

参考
Date.prototype.getTime() - JavaScript | MDN


◼︎1秒間待つ

var time = new Date().getTime();
while (new Date().getTime() < time + 1000);


◼︎実行時間の計測に用いる

var end,
    start;

start = new Date();

for (var i = 0; i < 1000; i++) {
  Math.sqrt(i);
}

end = new Date();

console.log("Operation took " + (end.getTime() - start.getTime()) + " msec");