i need to create some kind of elementary pos with javascript. I have an barcode scanner that work like a keyboard. So i want to automaticaly detect when the input come from the barcode and then create a report with that codes. I think an good idea is to calculate the difference of typing speed because the scanner is really fast:
if there a dalay between keyup > 300ms = another scan
var speed = new Date().getTime() - lastkey;
lastkey = (new Date()).getTime();
console.log(speed);
if(speed > 300) {
//little delay for prevent computer overhead o_O
var create_d = setTimeout(createchange,300)
} else {
//barcode sanning continue
clearTimeout(create_d)
}
JsFiddle link <
Using pure JS:
document.body.onkeydown = function ()
{
var time = this._time;
var timestamp = new Date().getTime();
if (time)
console.log(timestamp - time);
this._time = timestamp;
}
The console will display difference between keydown events (in ms)
Related
I am trying to create a Countup counter Starting from 1 to 10000 and i do not want it to reset when user refreshes the page or cancels the page. The Counter should start from 1 for every user that visits the page and keep running in background till it gets to 10000 even if the page is closed.
I have written the page below which;
Starts from the specified number for every new visitor
Saves the progress and does not reset when page is refreshed, however
It does not keep counting when page is closed and starts from the last progress when user closes the tab and comes back later. My code is
function countUp() {
var countEl = document.querySelector('.counter');
var countBar = document.querySelector('.progress-bar');
var x = parseInt(localStorage.getItem('lastCount')) - 1 || 1;
var y = countEl.dataset.to;
var z = countBar.dataset.to;
function addNum() {
countEl.innerHTML = x;
x += 1;
if (x > y && x > z) {
clearInterval(timer);
}
localStorage.setItem('lastCount', x);
}
var timer = window.setInterval(addNum, 1000);
localStorage.setItem("addNum", counter);
toggleBtn.addEventListener('click', function(){
countUp();
toggleBtn.classList.add('hidden');
});
}
countUp();</script>
<body onload=countUp();>
<div class="counter" data-from="0" data-to="10000000"></div>
<div class="progress-bar" data-from="0" data-to="10000000"></div>
</body>
It's difficult to show an example on StackOverflow because it doesn't let you fiddle with localStorage but, it sounds like you want something like:
When a user visits the page check localStorage for a timestamp.
If timestamp exists, go to step 4
Timestamp doesn't exist so get the current timestamp and stash it in localStorage.
Get the current timestamp. Subtract the timestamp from before. If over 10,000, stop, you're done.
Display difference calculated in step 4.
Start a 1 second timer, when time is up, go to step 4.
Something along those lines should work even if they refresh the page and since you are calculating from the original timestamp it will "count" in the background even if the page is closed.
window.addEventListener("DOMContentLoaded", () => {
const start = localStorage.getItem("timestamp") || Date.now();
localStorage.setItem("timestamp", start);
function tick() {
const now = Date.now();
const seconds = Math.floor((now - start) / 1000);
const display = document.getElementById("display");
if (seconds > 10000) return display.innerHTML = "We're done";
display.innerHTML = seconds;
setTimeout(tick, 1000);
}
tick();
});
<div id="display"></div>
So, client-side code can't normally execute when a client-side javascript page is closed.
What you could do, however, is calculate where the timer should be then next time it is loaded.
For example, in your addNum() function, you could in addition to the last count, also store the current date (and time).
function addNum() {
countEl.innerHTML = x;
x += 1;
if (x > y && x > z) {
clearInterval(timer);
}
localStorage.setItem('lastCount', x);
localStorage.setItem('lastDate', new Date());
}
Then, when your code starts, you can retrieve lastDate, and then subtract the current Date() from it.
Then use that to add the difference to your counter.
function countUp() {
let storedCount = parseInt(localStorage.getItem('lastCount'));
let storedDate = Date.parse(localStorage.getItem('lastDate'));
let now = new Date()
let diffSeconds = (now.getTime() - storedDate.getTime()) / 1000;
let storedCount += diffSeconds;
var countEl = document.querySelector('.counter');
var countBar = document.querySelector('.progress-bar');
var x = storedCount - 1 || 1;
var y = countEl.dataset.to;
var z = countBar.dataset.to;
}
I'm sure there are some more changes required to make it work with your code, but the idea is to store the current time so that when the page is closed and reopened, you can 'adjust' the count to catch up to what it should be.
What you want here is not possible just from the client-side code, there is no way for 2 different machines to share that information at all.
Here's the thing though, you can do this with a backend where the database gets updated every time a new IP hits the server. Note with this approach, a user here is one system and not different browsers or sessions.
To update this real-time for someone who is already on the website, run a timer and call an API that specifically gives you the count. Therefore the page gets updated frequently. You can also do this with react-query as it comes with inbuilt functions to do all this.
if (document.case.display.value.length >16 && document.case.display.value.length < 21) {
Notiflix.Notify.Info('Because you have a lot of charatchers font size is smaller');
document.getElementById("display").style.fontWeight = "550";
document.getElementById("display").style.fontSize = "2em";
} else if (document.case.display.value.length > 20) {
var str = document.case.display.value.length
Notiflix.Notify.Warning('Max characters you can see is 25 ');
Notiflix.Notify.Failure('Number of your characters' + str);
document.getElementById("display").style.fontWeight = "500";
document.getElementById("display").style.fontSize = "1.5em";
}
else {
document.getElementById("display").style.fontWeight = "500";
document.getElementById("display").style.fontSize = "2.5em";
}}
window.setInterval(function(){
testLength();
}, 100);
Notiflix is a JavaScript library for notification.
I have a display who font go down if have so much characters and i set time every 0.1 second he check number of characters. If number is higher than 16 he put a notification.
But he put every 0.1 second notification i want only one time/s. Do you have idea who can "block " this line of code for 10 second and after that read this without moving settimer down.
Sorry about bad English.
Any information will help me
You can try storing your setInterval() in a variable and calling it only when required. Else, you can stop that using that variable name.
let myInterval;
function start(){
myInterval = window.setInterval(function(){
testLength();
}, 100);
}
function stop(){
clearInterval(myInterval);
}
P.S: I would also like to advice on using onChange eventListener for checking test length rather than setInterval.
Update: Alternate method
You can also try removing setInterval thing and adding something like this:
document.addEventListener("DOMContentLoaded", function(event) {
var numbers = document.querySelectorAll(".digit")
console.log("numbers", numbers);
numbers.forEach(el => el.addEventListener('click', testLength))
});
I am learning javascript and at the same time trying to create a simple script that allows you to type a foreign language on a web browser with your keyboard.
So, when you type a for example, there is a single letter mapped to a, so a single character Դ would appear, however to make a character like 厄 appear, you have to type twice, since this language has more characters than the English alphabet.
So, the problem is with that last character. Normally, I should have to type g and h consecutively in the span of one second to produce the 厄 letter, but I have problems waiting to check if within two characters have been typed within one second of eachother inorder to show that letter.
So, I don't think time interval functions are the way to go about this, but I can't see any other method also.
cautions: check key whether up in keydown() & notify keydown the key is upped in keypress();
var start = null;
$('#in').keydown(function (e) {
if (!start) {//checking is a new user input
start = $.now();
}
}).keyup(function (e) {
var timeElapsed = $.now() - start;
start = null;//start the next timing tracking
console.log(['time elapsed:', timeElapsed, 'ms'].join(' '));
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<label>
<h2>please input some letter to test</h2>
<input id="in"/>
</label>
another answer about your question,perhaps this is your truly answer.
function duration(timestamps) {
var last = timestamps.pop();
var durations = [];
while (timestamps.length) {
durations.push(last - (last = timestamps.pop()));
}
return durations.reverse();
}
function display(mills) {
if (mills > 1000)
return (mills / 1000) + ' s';
return mills + ' ms';
}
var durations = [];
$('#in').keydown(function (e) {
durations.push($.now());
}).keyup(function (e) {
var current = durations;
current.push($.now());
durations = [];
var timeElapsed = current[current.length - 1] - current[0];
console.log([
['time elapsed:', display(timeElapsed)].join(' '),
['keys duration:', duration(current).map(display)].join(' ')
].join(' --- '));
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<label>
<h2>Please input something to test!</h2>
<input id="in"/>
</label>
Below is the sample code to measure the elapsed time between any 2 events.
I added setTimeout just to give you an example.
var startTime = Date.now();
setTimeout(function(){
var elapsedTime = Date.now() - startTime;
console.log('elapsedTime ='+elapsedTime);
}, 100);
Like Alex mentioned, for every press, simply store new Date().getTime(); in a variable, which will get you the latest UTC time. UTC time is given in milliseconds, so on the next key-press, just see if the current time and the stored time differ by 1000!
I'm using NodeJs.
I received constantly request from server.
I'm added some variable like createdTime to it and saved to the database.
when I sorted data by createdTime in some case It is not reliable, It is Repeated
How can I make differentiate between them ?
I do not want to count request.
I do not like to change timestamp's format.
var createdTime = new Date().getTime();
Here's a method of combining a counter with the current time to allow you to have as many as 1000 separate transactions within the same ms that are all uniquely numbered, but still a time-based value.
And, here's a working snippet to illustrate:
// this guarantees a unique time-based id
// as long as you don't have more than 1000
// requests in the same ms
var getTransactionID = (function() {
var lastTime, counter = 0;
return function() {
var now = Date.now();
if (now !== lastTime) {
lastTime = now;
counter = 0;
} else {
++counter;
}
return (now * 1000) + counter;
}
})();
for (var i = 0; i < 100; i++) {
document.write(getTransactionID() + "<br>");
}
If you want something that is likely to work across clusters, you can use process.hrtime() to use the high resolution timer instead of the counter and then make the id be a string that could be parsed into a relative time if needed. Since this requires node.js, I can't make a working snippet here in the browser, but here's the idea:
// this makes a unique time-based id
function getTransactionID () {
var now = Date.now();
var hrtime = process.hrtime();
return now + "." + ((hrtime[0] * 1e9) + hrtime[1]);
}
Due to my low rep I can't add a comment but it looks like you are needing to go beyond milliseconds.Maybe this stackoverflow question can help you
How to get a microtime in Node.js?
I'm looking for a way to manipulate animation without using libraries
and as usual I make a setTimeout in another setTimout in order to smooth the UI
but I want to make a more accurate function to do it, so if I want to make a 50ms-per-piece
animation, and I type:
............
sum=0,
copy=(new Date()).getMilliseconds()
function change(){
var curTime=(new Date()).getMilliseconds(),
diff=(1000+(curTime-copy))%1000 //caculate the time between each setTimeout
console.log("diff time spam: ",diff)
sum+=diff
copy=curTime
var cur=parseInt(p.style.width)
if (sum<47){//ignore small error
//if time sum is less than 47,since we want a 50ms-per animation
// we wait to count the sum to more than the number
console.log("still wating: ",sum)
}
else{
//here the sum is bigger what we want,so make the UI change
console.log("------------runing: ",sum)
sum=0 //reset the sum to caculate the next diff
if(cur < 100)
{
p.style.width=++cur+"px"
}
else{
clearInterval(temp)
}
}
}
var temp=setInterval(change,10)
I don't know the core thought of my code is right,anyone get some ideas about how to make a more accurate timer in most browser?
Set the JsFiddle url:
http://jsfiddle.net/lanston/Vzdau/1/
Looks too complicated to me, use setInterval and one start date, like:
var start = +new Date();
var frame = -1;
var timer = setInterval(checkIfNewFrame, 20);
function checkIfNewFrame () {
var diff = +new Date() - start;
var f = Math.floor(diff / 50);
if (f > frame) {
// use one of these, depending on whether skip or animate lost frames
++frame; // in case you do not skip
frame = f; // in case you do skip
moveAnimation();
}
}
function moveAnimation () {
... do whatever you want, there is new frame, clear timer past last one
}