Timer: setTimeout and function call - javascript

function tick() {
seconds_lapsed++; // Break point.
}
function countdown() {
while(!stopped || !is_paused()){
setTimeout(tick, 1000); // 1 second.
show_counter();
}
}
Could you tell me why the interpreter doesn't stop at the breakpoint? The while loop works, hava a look at the screenshot.

The while loop is a "busy" loop, i.e. it keeps the JavaScript engine busy, so it will not process anything that is waiting in one of its event/job queues. This means that the user interface does not get updated, no input can be processed, and events produced by setTimeout are not consumed. In this example, tick can only get executed if the currently running code finishes. So the while loop must end first.
You should let tick execute, and only then check the condition:
var stopped = true;
var seconds_lapsed = 0;
document.querySelector("button").addEventListener("click", function() {
stopped = !stopped;
seconds_lapsed = 0;
this.textContent = stopped ? "Start" : "Stop";
if (!stopped) countdown();
});
function show_counter() {
document.querySelector("span").textContent = seconds_lapsed;
}
function is_paused() {
return document.querySelector("input").checked;
}
function tick() {
seconds_lapsed++;
}
function countdown() {
show_counter();
setTimeout(function () {
if (stopped) return; // stop the loop
if (!is_paused()) tick();
countdown(); // <--- this is the "loop"
}, 1000);
}
Seconds elapsed: <span>0</span><br>
<input type="checkbox">Paused<br>
<button>Start</button>

the following example might help you accomplish what you are after. Distinguish between setInterval() and setTimeout()
Basically the docs say:
setTimeout executes a function or specified piece of code once the timer expires.
setInterval repeatedly calls a function or executes a code snippet, with a fixed time delay between each call.
So if you use setInterval you don't need a while loop inside because it is already called "repeatedly"
var counter = $('#counter');
var stopped = false;
var seconds_lapsed=0;
var myInterval;
function tick() {
if(stopped) {
clearInterval(myInterval);
show_counter('FINISHED');
return;
}
show_counter(seconds_lapsed++);
}
function show_counter(message){
counter.html(message);
}
function countdown() {
myInterval = setInterval(tick, 1000);
}
function endCountdown(timeout) {
let timeoutId = setTimeout(function(){
stopped = true;
clearTimeout(timeoutId)
}, timeout);
}
countdown(); // start the countdown
endCountdown(5000); // ends the countdown after 5000 ms => 5sec
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="counter">counter</div>

Related

Node.js use setInterval & clearInterval on a function

Hello is there a way to call a function with setInterval and clear the interval later?
Example: When I write in a chat !start the interval function should start with a interval. And when I write !stop in the chat the function with the interval on it should stop.
This is my function:
function abb(channel){
console.log('Auto-Ban-Bot Timer running...')
getChannelViewers(channel.replace('#','')).then(
promise => {
var vierwernames = promise.chatters.viewers;
vierwernames.forEach(element => {
checkFriendlyBots(element)
});
}
);
}
I've tried many things but only got the !start command working, not the !stop command.
This is exactly what clearInterval() method does. It clears a timer set with the setInterval() method.
Check out this example:
const interval = setInterval(myTimer, 1000);
let i = 0;
function myTimer() {
console.log(i++);
if (i === 5){
stop();
}
}
function stop() {
clearInterval(interval);
}

clearTimeout not working: parameter undefined(even though it's defined in the global scope)

My setTimeout() function works, but my clearTimeout() is not working. Even though I have an 'if' statement that's supposed to run the clearTimeout function once my variable 'secs' is less than 0, the timer keeps counting down into negative numbers. When I type my variable name, 'secs' into the console, I get undefined, even though it's defined as a parameter in the function called by my setTimeout. I don't know what I'm doing wrong. Can anyone help, please?
My full code is at https://codepen.io/Rburrage/pen/qBEjXmx;
Here's the JavaScript snippet:
function startTimer(secs, elem) {
t = $(elem);
t.innerHTML = "00:" + secs;
if(secs<0) {
clearTimeout(countDown);
}
secs--;
//recurring function
countDown = setTimeout('startTimer('+secs+',"'+elem+'")', 1000);
}
Add a condition to call recursive function like below.
if (secs < 0) {
secs = secsInput;
}
//recurring function
countDown = setTimeout('startTimer('+secs+',"'+elem+'")', 1000);
For a countdown timer, I would recommend using setInterval and clearInterval instead. setInterval will repeatedly run the callback function for you. It might look like this:
let countdown;
function startTimer(secs, elem) {
countdown = setInterval(function(){
t = $(elem);
t.innerHTML = "00:" + secs;
secs--
if (secs < 0) {
clearInterval(countdown);
}
}, 1000);
}
By the time you call clearTimeout(countDown), countDown refers to the previous timeout, that already timed out. It will not stop the one yet to start. You could just not re set the timeout, like
if(!/*finished*/) setTimeout(startTimer, 1000, secs, elem);
In your case, it's more convenient to use setInterval and clearInterval.
To keep the setTimeout and clearTimeout functions, you should add return in the if statement.
function startTimer(secs, elem) {
t = $(elem);
t.innerHTML = "00:" + secs;
if(secs<0) {
clearTimeout(countDown);
return;
}
secs--;
//recurring function
countDown = setTimeout('startTimer('+secs+',"'+elem+'")', 1000);
}
So there are 4 events in my opinion that will have to be addressed by the timer:
The quiz starts
The quiz ends
The timer runs out
The player answers a question
This can be solved by a function returning an object with some options.
The createTimer can be used to set the parameters for the timer.
Point 1. would be timer.start() --> will start a timer with the parameters
Point 3. can be addressed with the callback that will be called if the timer runs out --> createTimer(5,'display', ()=>{ // your code goes here })
Point 2. can be achieved with --> timer.stop()
Point 4. is needed when the timer needs to be reset without running out timer.reset()
Further on the interval is not in the global scope so you could have multiple timers with different settings and they wouldn't interfere with each other
// function for creating the timer
function createTimer(seconds, cssSelector, callbackOnTimeout) {
// interval the timer is running
let interval;
// the html node where innerText will be set
const display = document.getElementById(cssSelector)
// original seconds passt to createTimer needed for restart
const initSec = seconds
// starting or continuing the interval
function start() {
// setting interval to the active interval
interval = setInterval(() => {
display.innerText = `00:${seconds}`;
--seconds;
if (seconds < 0) {
// calling restart and callback to restart
callbackOnTimeout()
restart()
}
}, 1000);
}
// just stopping but not resetting so calling start will continue the timer
// player takes a break
function stop(){
clearInterval(interval)
}
// opted for a restart and not only a reset since it seemed more appropriate for your problem
function restart(){
clearInterval(interval)
seconds = initSec
start()
}
// returning the object with the functions
return {
start: start,
stop: stop,
restart: restart
}
}
// example for creating a timer
const timer1 = createTimer(5,'display',()=>{
console.log(`you where to slow ohhh...`)
})
// calling the timer
timer1.start()

Using setInterval to Save Form Every 60 Seconds Not Working

I'm working on some code that'd I'd like to have each loop run every 60 seconds, but currently each loop runs immediately. The purpose of the code it to see if a form has changed, and if it has save the form. Do I have setInterval setup incorrectly?
function saveHelper(formId) {
for(var i = 0; i < 4; i++) {
save(formId);
}
}
function save(formId) {
console.log('might save');
var changed = formChanges(formId);
var intId = setInterval(stall, 60000);
if(changed.length > 0) {
console.log('would save');
//document.getElementById(formId).submit();
}
clearInterval(intId);
}
function stall() {
return true;
}
You are treating interval as some sort of synchronous sleep method, which is not the case. The change code should be inside of the setInterval, it should not live after the interval.
var intId = setInterval(function () {
if(changed.length > 0) {
console.log('would save');
//document.getElementById(formId).submit();
}
}, 60000);
setInterval doesn't pause your code, it just schedules some code to be run some time in the future. For example, when you do this:
var intId = setInterval(stall, 60000);
That says "every 60000 milliseconds, run the function stall". As soon as this line of code completes, it will immediately run your next line of code, do the saving, then clear the interval. Clearing the interval cancels it, so now nothing will happen in 60000 milliseconds.
Instead, you'll want to do something like this:
function saveHelper(formId) {
let count = 0;
const intId = setInterval(function () {
if(changed.length > 0) {
console.log('would save');
//document.getElementById(formId).submit();
}
count++;
if (count === 4) {
clearInterval(intId);
}
}, 60000);
}
Every 60000 milliseconds, the inner function will run, and do the saving. After saving, it checks how many times we've done this, and once it reaches 4, it clears the interval to stop it from happening any more.

Can I stop the execution of a function from outside that function?

I have this code:
function toStop(){
while(true){}
}
toStop();
Now, how can I stop this? Or how can I kill the current thread if this function call is somewhere in the setInterval running thread? Example:
var id = setInterval(function(){
toStop();
}, 1000);
//stop thread/timer with id here.
clearInterval doesn't work because it waits until the function call ends.
Thanks!
"Can I stop the execution of a function from outside that function?"
No, you can't programmatically.
JavaScript is single-threaded and if you run a piece of code that makes it infinitely busy, such as while(true);, then nothing else will ever be able to execute.
Calling such a piece of code within setTimeout or setInterval will have the same result, since the callback of these gets executed in the only thread we have as well.
However, you can create a timed recurring execution using setInterval or setTimeout, which can be stopped.
var timerId = setInterval(function () {
//Process an iteration of the loop in here
//If you cause an infinite loop in here, you will have the same issue
}, 50);
//stop the timer after ~3 seconds
setTimeout(clearInterval.bind(null, timerId), 3000);
Notes:
4 is the lowest interval that could be honored as specified in the SPEC.
setInterval will stack if the callback takes more time to execute than the specified interval. For that reason I never use setInterval and always use setTimeout.
Timer intervals are not guaranteed to be accurate
e.g. with setTimeout
var stopProcessing = startProcessing();
//Stop processing after ~3 seconds
setTimeout(stopProcessing, 3000);
function startProcessing() {
var timerId;
!function process() {
//Do some processing
//Continue processing in ~50 ms
timerId = setTimeout(process, 50);
}();
return function () { clearTimeout(timerId); }
}
Instead of an infinite loop, just use an if statement and wrap it in an interval:
var shouldContinue = true;
var interval = 0;
function toStop() {
if (interval == 0) {
interval = setInterval(function() {
if(shouldContinue) {
...
}
else {
clearInterval(interval);
interval = 0;
}
}, 200); // Or whatever interval makes sense
}
}
toStop();
// ...
shouldContinue = false;
See this principle in action here.
No, you can't programmatically, as #plalx said but you could try this: declaring a binding outside and check on that to continue or stop the loop:
let letMeGoOut;
function toStop(){
while(letMeGoOut != false)
}
toStop();
Here, I've created a function on mouseover that triggers a loop changing the opacity of the h1. It goes on till the mouse cursor moves out and is over something else in the page.
Here is the example: https://codepen.io/Mau-Di-Bert/pen/VqrRxE

Pause JS function from another function

Is there any way I can pause the below set of delayed functions from another function? I want to pause everything for 10 seconds by executing another function.
What I need is something like:
function pause(){
pause sleepLoop() for 10 seconds
}
If it is not possible to pause the below execution, can I kill it?
function game() {
sleepLoop();
}
function sleepLoop() {
loop...
setTimeout('gameActions()',5000);
}
function gameActions() {
actions...
sleepLoop();
}
Store the timer in a variable. Then you can stop it with clearTimeout, and restart it after 10 seconds:
function game() {
sleepLoop();
}
var sleepLoopTimeout;
function sleepLoop() {
gameActions();
sleepLoopTimeout = setTimeout(sleepLoop,5000);
}
function pause(){
clearTimeout(sleepLoopTimeout);
setTimeout(sleepLoop, 10000);
}
function gameActions() {
// Actions
}
var gameTimeout, sleepTimeout;
function game() {
gameTimeout = setTimeout(sleepLoop, 10000); //start in 10 seconds
}
function sleepLoop() {
sleepTimeout = setTimeout(gameActions, 5000); //start in 5 secs
}
function gameActions() {
sleepLoop();
}
//start it off:
game();
Other than the above, I am not sure what you are asking.
To kill (clear) the timeouts:
clearTimeout(gameTimeout);
clearTimeout(sleepTimeout);
var blocked = false;
function loopToBePaused()
{
if (blocked !== false)
{
// will check for blocker every 0.1s
setTimeout(loopToBePaused, 100);
return;
}
// payload
// normal loop now, e.g. every 1s:
setTimeout(loopToBePaused, 1000);
}
// somewhere in code run:
blocked = setTimeout(function() {
// blocking our loop'ed function for 10s
blocked = false;
}, 10000);
// this will block our main loop for 10s

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