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Discussion on: JavaScript Functions That Will Make Your Life Much Easier [Updatable].

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krimfandango profile image
Kareem Kamal • • Edited

Hello, nice list!

runEvery function is broken, it runs a script every x milliseconds if hour is after the given hour and minute is after the given minute, so given this input:

runEvery(() => console.log('ran'), 12, 30, 300000)
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and the time now is 3:17 PM it will try running at 8:17 PM but now.getMinutes() >= mins will return false and the function will not execute, and every 5 hours it will always return false
But if you set minutes to 0 or someone starts the application after the provided minute it will execute every interval after the given time.

If the goal is to make a function that runs every day at a certain time, you need to get the time to the next occurrence and start the interval then, something like this:

function runEverydayAt(callback, hour, minute) {
  // first we need to get the time until the next hour:minute
  const now = new Date()
  // to check if the next time happens today check how many minutes
  // passed in the day and compare them with the input
  const nowInMinutes = (now.getHours() * 60) + now.getMinutes()
  const inputTimeInMinutes = (hour * 60) + minute
  const isNextTimeToday = nowInMinutes < inputTimeInMinutes

  // create a new date for the comparison
  const firstTime = new Date()
  // and set its time to the input's time
  firstTime.setHours(hour, minute, 0)

  if (!isNextTimeToday) {
    // if next time is today then add a day
    firstTime.setDate(now.getDate() + 1)
  }

  const timeUntilNextOccurrence = firstTime.getTime() - now.getTime()

  // finally set a timeout to start the first call
  // on time then every other call every 24 hours
  setTimeout(() => {
    // setInterval will start kicking in after 24 hours
    // therefore we need to invoke the first callback here
    callback()
    setInterval(callback, 1000 * 60 * 60 * 24)
  }, timeUntilNextOccurrence)
}

// to check you can try invoking it with a time that's coming soon
runEverydayAt(() => console.log('I ran!'), 10, 43)
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youssefzidan profile image
Youssef Zidan •

Great!
Thanks for your feedback!
I'll check my code again and get back to you.

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youssefzidan profile image
Youssef Zidan • • Edited

Hello!
I tried to run your function but it doesn't seem to be working.

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krimfandango profile image
Kareem Kamal •

Hey Youssif, I've just tried running the code in the console and it seems to be working.
You just need to set the time to be coming up in a minute or two so that you wouldn't wait for long for the next occurrence

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