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How do I trigger a function when the time reaches a specific time in JavaScript?


For this, extract the time of specific date time and call the function using setTimeout(). The code is as follows −

Example

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initialscale=1.0">
<title>Document</title>
<link rel="stylesheet" href="//code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">
<script src="https://code.jquery.com/jquery-1.12.4.js"></script>
<script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/fontawesome/4.7.0/css/font-awesome.min.css">
<style>
</style>
</head>
<body>
<script>
   function timeToAlert() {
      alert("The time is 9:36 AM");
   }
   var timeIsBeing936 = new Date("08/09/2020 09:36:00 AM").getTime()
   , currentTime = new Date().getTime()
   , subtractMilliSecondsValue = timeIsBeing936 - currentTime;
   setTimeout(timeToAlert, subtractMilliSecondsValue);
</script>
</body>
</html>

To run the above program, save the file name “anyName.html(index.html)” and right click on the file. Select the option “Open with Live Server” in VS Code editor.

Output

This will produce the following output −

How do I trigger a function when the time reaches a specific time in JavaScript?