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How many seconds has passed today?

importance: 5

Write a function getSecondsToday() that returns the number of seconds from the beginning of today.

For instance, if now 10:00 am, and there was no daylight savings shift, then:

getSecondsToday() == 36000 // (3600 * 10)

The function should work in any day. That is, it should not have a hard-coded value of “today”.

To get the number of seconds, we can generate a date using the current day and time 00:00:00, then substract it from “now”.

The difference is the number of milliseconds from the beginning of the day, that we should divide by 1000 to get seconds:

function getSecondsToday() {
  let now = new Date();

  // create an object using the current day/month/year
  let today = new Date(now.getFullYear(), now.getMonth(), now.getDate());

  let diff = now - today; // ms difference
  return Math.round(diff / 1000); // make seconds
}

alert( getSecondsToday() );

An alternative solution would be to get hours/minutes/seconds and convert them to seconds:

function getSecondsToday() {
  let d = new Date();
  return d.getHours() * 3600 + d.getMinutes() * 60 + d.getSeconds();
};