Develop Reference

HTML or Javascript for switching url at a specific time

I am from Germany, sorry for my English.
I am searching for a simple HTML or Javascript code to switch to another URL at a specific time.
I Run a landing Page which has an offer thats closed at April 16 at ten o clock for example. I need a little Script or code which directs to another url when the öfter will be closed.
I am thankful for any help.
Best regards
Marco

If the person has the landing page loaded and is viewing it, and you want to send them to a different URL when the offer closes, you can calculate how much time until that happens when they arrive at the landing page then send them to the new URL when that time is reached.
setTimeout will run a function after a timer has expired, and that function can change the window.location sending them to the new URL.
When the landing page loads get the current time and the time the offer expires:
let now = new Date();
let expires = new Date('2021-04-16 22:00:00');
Subtracting gives you the number of milliseconds until you reach the expires time, which is convenient because that's what the setTimeout function wants for it's "delay" parameter.
Verbosely, this could look like:
const now = new Date();
const expires = new Date('2021-04-16 22:00:00');
const delay = expires - now;
window.setTimeout(function() {
window.location = 'https://example.com/';
}, delay);
<div>
<p>This is the landing page</p>
</div>
This does not loop waiting for time to expire, as DCR warns in a comment; it just sets a timer, which the browser then takes care of.
All the math could be collapsed without using variables, so it becomes
window.setTimeout(function() {...etc...}, new Date('2021-04-16 22:00:00') - new Date());

Here is your script based on your mentioned time. After that specific time, link will be changed automatically.
"https://jsfiddle.net/rounak1/2pxLu5df/2/"

here is the code
let d1 = new Date()
var d2 = new Date('2021-04-16 22:00:00.00');
if (d1 > d2) {
window.location = 'https://www.google.com/'
}

I believe that this problem is better handled by your backend that can redirect the user to another page before the page loads since, if you do this in javascript, the page will have to load first.
However, since you want this to be implemented in Javascript you can do something like below:
var time = moment("16/04/2021 10:00", "DD/MM/YYYY HH:mm");
var now = new Date();
if (time > now) {
window.location.replace("replace with your url"); // Without allowing the user to hit the back button
}
In the above, time stores the datetime when the offer ends in the format enclosed as a string (read about this here: https://momentjs.com/docs/#/parsing/string-format/). This is compared to the time now to implement a redirect.
Read more about the redirect here: https://www.w3schools.com/howto/howto_js_redirect_webpage.asp
The above requires the usage of the moment.js library which you can find here: https://momentjs.com/

page speed metrics on javascript [duplicate]

I am trying to make a webpage that, when it starts loading, uses an Interval to start a timer.
When the page fully loads, it stops the timer,
but 99% of the time i get time measurements of 0.00 or 0.01 even if it takes longer.
Occasionally, it says something that makes more sense like .28 or 3.10 at some times.
Here is the code if it helps:
var hundredthstimer = 0;
var secondplace = 0;
function addinc(){
hundredthstimer += 1;
if (inctimer == 100){
hundredthstimer = 0;
secondplace += 1;
}
}
var clockint = setInterval(addinc, 10);
function init(){
var bconv1 = document.getElementById("bconverter1");
var bconv2 = document.getElementById("bconverter2");
$(bconv2).hide();
clearInterval(clockint);
if (inctimer.len !== 2){
inctimer = "0" + inctimer;
}
alert(secondplace + "." + inctimer);
}
onload = init;
So it basically creates a variable called hundredthstimer which is increased by '1' every 10 miliseconds(.01 seconds).
Then, if this number reaches 1000(1 full second), a variable called secondsplace goes up by 1, since that is how many full seconds it has run for.
Then, it alerts secondsplace, a decimal point, and hundredthsplace as the total load time.
But the problem above with incorrect numbers still exists. Why?

Why so complicated? When you can do:
var loadTime = window.performance.timing.domContentLoadedEventEnd- window.performance.timing.navigationStart;
If you need more times check out the window.performance object:
console.log(window.performance);
This will show you the timing object:
connectEnd Time when server connection is finished.
connectStart Time just before server connection begins.
domComplete Time just before document readiness completes.
domContentLoadedEventEnd Time after DOMContentLoaded event completes.
domContentLoadedEventStart Time just before DOMContentLoaded starts.
domInteractive Time just before readiness set to interactive.
domLoading Time just before readiness set to loading.
domainLookupEnd Time after domain name lookup.
domainLookupStart Time just before domain name lookup.
fetchStart Time when the resource starts being fetched.
loadEventEnd Time when the load event is complete.
loadEventStart Time just before the load event is fired.
navigationStart Time after the previous document begins unload.
redirectCount Number of redirects since the last non-redirect.
redirectEnd Time after last redirect response ends.
redirectStart Time of fetch that initiated a redirect.
requestStart Time just before a server request.
responseEnd Time after the end of a response or connection.
responseStart Time just before the start of a response.
timing Reference to a performance timing object.
navigation Reference to performance navigation object.
performance Reference to performance object for a window.
type Type of the last non-redirect navigation event.
unloadEventEnd Time after the previous document is unloaded.
unloadEventStart Time just before the unload event is fired.
Browser Support
More Info

Don't ever use the setInterval or setTimeout functions for time measuring! They are unreliable, and it is very likely that the JS execution scheduling during a documents parsing and displaying is delayed.
Instead, use the Date object to create a timestamp when you page began loading, and calculate the difference to the time when the page has been fully loaded:
<doctype html>
<html>
<head>
<script type="text/javascript">
var timerStart = Date.now();
</script>
<!-- do all the stuff you need to do -->
</head>
<body>
<!-- put everything you need in here -->
<script type="text/javascript">
$(document).ready(function() {
console.log("Time until DOMready: ", Date.now()-timerStart);
});
$(window).load(function() {
console.log("Time until everything loaded: ", Date.now()-timerStart);
});
</script>
</body>
</html>

The answer mentioned by #HaNdTriX is a great, but we are not sure if DOM is completely loaded in the below code:
var loadTime = window.performance.timing.domContentLoadedEventEnd- window.performance.timing.navigationStart;
This works perfectly when used with onload as:
window.onload = function () {
var loadTime = window.performance.timing.domContentLoadedEventEnd-window.performance.timing.navigationStart;
console.log('Page load time is '+ loadTime);
}
Edit 1: Added some context to answer
Note: loadTime is in milliseconds, you can divide by 1000 to get seconds as mentioned by #nycynik

It is hard to make a good timing, because the performance.dominteractive is miscalulated (anyway an interesting link for timing developers).
When dom is parsed it still may load and execute deferred scripts. And inline scripts waiting for css (css blocking dom) has to be loaded also until DOMContentloaded. So it is not yet parsed?
And we have readystatechange event where we can look at readyState that unfortunately is missing "dom is parsed" that happens somewhere between "loaded" and "interactive".
Everything becomes problematic when even not the Timing API gives us a time when dom stoped parsing HTML and starting The End process. This standard say the first point has to be that "interactive" fires precisely after dom parsed! Both Chrome and FF has implemented it when document has finished loading sometime after it has parsed. They seem to (mis)interpret the standars as parsing continues beyond deferred scripts executed while people misinterpret DOMContentLoaded as something hapen before defered executing and not after. Anyway...
My recommendation for you is to read about​ Navigation Timing API. Or go the easy way and choose a oneliner of these, or run all three and look in your browsers console ...
document.addEventListener('readystatechange', function() { console.log("Fiered '" + document.readyState + "' after " + performance.now() + " ms"); });
document.addEventListener('DOMContentLoaded', function() { console.log("Fiered DOMContentLoaded after " + performance.now() + " ms"); }, false);
window.addEventListener('load', function() { console.log("Fiered load after " + performance.now() + " ms"); }, false);
The time is in milliseconds after document started. I have verified with Navigation​ Timing API.
To get seconds for exampe from the time you did var ti = performance.now() you can do parseInt(performance.now() - ti) / 1000
Instead of that kind of performance.now() subtractions the code get little shorter by User Timing API where you set marks in your code and measure between marks.

here's an expression that gives the exact value:
window.performance.timing.loadEventEnd-window.performance.timing.navigationStart

Why does setInterval not increment my clock properly in JavaScript?

I want to display the actual time in New York. I have a html div:
<div id="time"></div>
and also - I have a php script that returns the actual time:
<?php
date_default_timezone_set('UTC');
echo time();
?>
and it does it as a timestamp.
Now, I've created a js script:
var serverTime;
moment.tz.add('America/New_York|EST EDT|50 40|0101|1Lz50 1zb0 Op0');
function fetchTimeFromServer() {
$.ajax({
type: 'GET',
url: 'generalTime.php',
complete: function(resp){
serverTime = resp.responseText;
function updateTimeBasedOnServer(timestamp) { // Take in input the timestamp
var calculatedTime = moment(timestamp).tz("America/New_York");
var dateString = calculatedTime.format('h:mm:ss A');
$('#time').html(dateString + ", ");
};
var timestamp = serverTime*1000;
updateTimeBasedOnServer(timestamp);
setInterval(function () {
timestamp += 1000; // Increment the timestamp at every call.
updateTimeBasedOnServer(timestamp);
}, 1000);
}
})
};
fetchTimeFromServer();
setInterval(function(){
fetchTimeFromServer();
}, 5000);
and the idea behind it is that I want to fetch the data from server, display it on my webpage, then increment it every second for five seconds and then fetch the time from the server again (to keep consistence with time on the server). And later on - continue with doing so, fetching the time, incrementing it for 5 seconds, fetching it again, etc.
It works... almost. After the webpage stays open for some time I can see the actual time, but it 'blinks', and I can see that it shows different times - it's hard to explain, but it looks like there is some time already in that div and new time tries to overlay it for each second. Seems like the previous time (content of this div) is not removed... I don't know how to create a jsfiddle with a call to remote server to fetch time from php, so I only have this information pasted above :(
What might be the problem here?

Since javascript is single threaded, setInterval may not acutally run your function after the delay. It adds the function to the stack to be run as soon as the processor is ready for it. If the processor has other events in the stack, it will take longer than the interval period to run. Multiple intervals or timeouts are all adding calls to the same stack for processing. To address this, you could use HTML5 web workers or try using setTimeout recursively.
Here is a good read on web workers: https://msdn.microsoft.com/en-us/hh549259.aspx

How to reload page when jquery.counter trigger finish.countdown event for multiple instance?

I am using multiple instance for jQuery countdown and implement page reload when counter get finished
E.g.
$('.countdown').each(function() {
var $this = $(this),
finalDate = $(this).data('countdown');
$this.countdown((finalDate), function(event) {
var days = event.strftime('%D');
$(this).find('.days').children('span').html(days);
$(this).find('.hours').children('span').html(event.strftime('%H'));
$(this).find('.minutes').children('span').html(event.strftime('%M'));
$(this).find('.seconds').children('span').html(event.strftime('%S'));
});
$(this).on('finish.countdown', function(event){
/*if(!window.location.hash && !(window.location.hash.indexOf('_loaded') > -1)) {
window.location = window.location + '#_loaded'; window.location.reload();
}*/
//If I put window location reload here it will goes into infinite loop. Also above commented code will reload page twice initially which is also not valid solution.
});
});
Issue: If countdown is already finished (E.g. 00:00:00:00 ) then page reload occur twice when script loaded at first time,
I have used localStorage concept but unable to find exact solution. Please help

I had almost this issue with page constantly reloading instantly.
Try and check if your local time and server time are the same. In my case, the difference was two hours, which was the issue that put the page into constant loop.
Countdown plugin has some notes on timezone awareness: http://hilios.github.io/jQuery.countdown/examples/timezone-aware.html

How to measures script execution and *parsing* time?

As far as I know, scripts are downloaded and executed synchronously in javascript.
Hence if we write the following code:
<script type='text/javascript'>console.time('core')</script>
<script type='text/javascript' src="guicore.js"></script>
<script type='text/javascript'>console.timeEnd('core')</script>
we'll see in console total time for download, parse and execute js.
How we can exclude parsing time? Just add similar file, but with all code commented out. More or less, this technique should work.
The problem is this just doesn't work =)
I optimized that code, reduce execution time from 90ms to 25ms, but see the same ~100±10ms time for Chrome and ~160±15ms for Firefox.
Ok, I know I could use profiler, but the question is: "how to measure js parsing time correctly" and what did I measured btw. Research.reverse-engineering is very fun, but maybe there's someone who knows that field in depth.

You cannot accurately measure script parse time independent of execution time using web APIs alone. Different browsers have different strategies for when they do parsing, and some of them will parse progressively as the script is executed, or even do "partial parsing" in cases where it's assumed a block of code is unlikely to immediately be executed (e.g. a function that is not an IIFE, see some details in the optimize-js README).
Using separate <script> tags is the most accurate way to at least capture both parsing and execution time. The only modification I would make to your snippet is this:
<script>
performance.mark('start');
</script>
<script src="myscript.js"></script>
<script>
performance.mark('end');
performance.measure('total', 'start', 'end');
</script>
Note the use of the high-precision User Timing API which, as an added bonus, will show visualizations in the Chrome/Edge/IE dev tools (and tools like Windows Performance Analyzer and WebPageTest if you're so inclined).
Technically the 3rd <script> is not necessary, as you can just append the mark/measure to the end of the 2nd script. But the 1st <script> is certainly necessary to capture all parse time. You can verify in the dev tools that the marks/measures encompass all initial parsing and execution time.

I know this is kind of an old question but I came across it while looking for a solution to this myself. You can use the dev tools in the browser of your choice to look at this but if you'd like to do it in code this is the method I ended up using.
The scriptLoadParseDuration function below will take a URL to a .js file, place it into a <script> element, and log the load/parse duration to the console.
Keep in mind that this will execute the <script> you are profiling within the current DOM context. So in the example below: jQuery is still accessible in the global scope even though the script was removed. The script could be extended to do all of this in an <iframe> to isolate it though.
function scriptLoadParseDuration(url) {
var start;
var script = document.createElement('script');
// <script> must be attached to the document to actually load the file
document.querySelector('html').appendChild(script);
// Calculate load/parse duration once script has loaded
script.addEventListener('load', function scriptLoad() {
// Calculate load/parse duration
console.log('Duration: ' + (Date.now() - start) + 'ms');
// Remove <script> from document
script.parentElement.removeChild(script);
}, false);
// Get current time in milliseconds
start = Date.now();
// Setting the `src` starts the loading. Math.random is used to make sure it is an uncached request
script.src = url + '?' + Math.floor(Math.random() * 9e9);
}
var url = 'https://code.jquery.com/jquery-3.0.0.min.js';
scriptLoadParseDuration(url);
Here is an example showing that jQuery is still in the global scope after the <script> removal.
function scriptLoadParseDuration(url) {
var start;
var script = document.createElement('script');
console.log('`jQuery` before attaching: ' + typeof jQuery);
// <script> must be attached to the document to actually load the file
document.querySelector('html').appendChild(script);
// Calculate load/parse duration once script has loaded
script.addEventListener('load', function scriptLoad() {
// Calculate load/parse duration
console.log('Duration: ' + (Date.now() - start) + 'ms');
console.log('`jQuery` once attached: ' + typeof jQuery);
// Remove <script> from document
script.parentElement.removeChild(script);
console.log('`jQuery` after detach: ' + typeof jQuery);
}, false);
// Get current time in milliseconds
start = Date.now();
// Setting the `src` starts the loading. Math.random is used to make sure it is an uncached request
script.src = url + '?' + Math.floor(Math.random() * 9e9);
}
var url = 'https://code.jquery.com/jquery-3.0.0.min.js';
scriptLoadParseDuration(url);

Open up Chrome and open the developer tools, the go to the "Timeline" tab. If you press the record button (filled in circle, bottom left) then reload the page it'll give you a fairly detailed timeline, broken down into specific types of activity (Send Request, Parse, Evaluate), timed down to the microsecond.

Very old question with a relatively new answer.
Date.now() returns a timestamp with millisecond accuracy. For an application to run at 60FPS, it must update the frame every 16ms. Our millisecond meter may not be accurate enough.
Introducing the Performace API in modern JS browsers, this allows for floating-point timestamps accurate to the microsecond.
Instead of Date.now() use window.performance.now() for measurements, there's a good guide on using the Performance API on HTML5Rocks.

Chrome DevTools actually has a hidden flag that shows V8 Parse and Compile time!
https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/javascript-startup-optimization#parsecompile
Outcome looks like this:
A quick guide is also available in the doc in the blue section below:
After you enable the feature, you can profile a page and then click on "Bottom-Up" tab on the Performance tab in Chrome DevTools, and then make sure you "Group by Activity", and you should see the Compile and Parse time now.
Enjoy!