Develop Reference

How to stop a function after ten seconds?

I found this piece of code while trying to find out a way to load a reddit page so that I can use ctrl + f to find a specific post. The problem is that it just keeps scrolling down and loading the pages. I need to find a way to stop it after 10 seconds so that I can take a look at what I loaded. Also I don't know any javascript so I couldn't really find anythig that would help me.
Here is the code
var lastScrollHeight = 0;
function autoScroll() {
var sh = document.documentElement.scrollHeight;
if (sh != lastScrollHeight) {
lastScrollHeight = sh;
document.documentElement.scrollTop = sh;
}
}
window.setInterval(autoScroll, 100);
I just paste that into the firefox console.

The setInterval() function returns an ID, which you can use to stop it.
Just put it in setTimeout() method like this:
var myInterval = setInterval(autoscroll, 100);
setTimeout(function(){ clearInterval(myInterval); }, 10000);

To stop the interval after a certain amount of time use a setTimeout() that calls clearInterval(). Here's a simplified version (with the time reduced to 1 second for demo purposes) that should help:
function autoScroll(){
console.log("running")
}
// save a reference to the interval handle
let interval = window.setInterval(autoScroll, 100);
// cancel interval after 1 second (1000 ms)
setTimeout(() => clearInterval(interval), 1000)

You will simply need to call clearInterval on your looped function to stop it after using a setTimeout set to 10 seconds, here is how you can implement it :
var lastScrollHeight = 0;
function autoScroll() {
var sh = document.documentElement.scrollHeight;
if (sh != lastScrollHeight) {
lastScrollHeight = sh;
document.documentElement.scrollTop = sh;
}
}
const interval = window.setInterval(autoScroll, 100);
window.setTimeout(() => {clearInterval(interval)}, 10000);

....
var intervalID = window.setInterval(autoScroll, 100);
setTimeout(function(){
clearInterval(intervalID);
}, 10000);

You can use setTimeout to call the function until 10s are up.
Here's an immediately-invoked function that calls itself every 100th sec until 10s has been reached.
(function autoScroll(t) {
t = t || 0;
if (t < 10000) {
console.log(t);
setTimeout(autoScroll, 100, t += 100);
}
})();

How to set a delay inside a for loop

So I have a for loop and there is one line of code in there that opens a URL for each other iterations. I would like that line that opens the URL to wait 2 seconds before opening each one. How would I do it?
I tried the setTimeout function, but it iterates through the whole loop instantly after waiting the specified seconds, but I want it to wait for each iteration, not just before the iteration or during the first one.
The structure of my code looks something like this:
function someFunction(){
// do something
for(i = 0; i < range; i++){
//do something
//**open URL**
//do something
}
}
How would I make it wait 2 seconds for every iteration before executing that one specific line where it opens the URL? None of the other questions seem to help me, so I was wondering if anyone could help.

You can use settimeout
function delayedFunction(counter){
counter--;
console.log(counter);
if(counter){
setTimeout(function(){delayedFunction(counter); }, 1000);
}
}
delayedFunction(5);

You cannot do this in a for loop. You can do this with setInterval(). The setInterval() method will continue until clearInterval() is called.
Structure
var interval = setInterval(function() {
var i = 0;
if(i < x) {
...
} else {
clearInterval(interval);
}
}, ms);
Example
var urls = ["url1", "url2", "url3", "url4"];
function showDelayed(arr, ms) {
var i = 0;
var interval = setInterval(function() {
if (i < arr.length) {
// Do something here
console.log(arr[i]);
} else {
clearInterval(interval); // Clear when i === arr.length
}
i += 1; // Interval increments 1
}, ms);
}
showDelayed(urls, 300);

Not that this is a very good practice (opening up multiple URLS on an interval),
but since you asked.
var urlarray = ["https://www.mysite1.com", "https://www.mysite2.com", "https://www.mysite3.com"];
var currentURL = 0;
setInterval(function() {
if (currentURL < urlarray.length) {
alert(urlarray[currentURL]);
}
currentURL++;
}, 1500);

Javascript setInterval for sequential numbers

I'm writing some code that looks like this
<script type="text/javascript">
setInterval(function write_numbers(){
var count = 1;
var brk = "<br>"
while (count < 1218){
document.write(count + brk);
count++;
}},1000)
</script>
I need it to display the first number which is one then wait one second then display the next number (2) then wait a second, I need this to carry on till it reaches 1218 then stop.
With the code I've written it just writes all the numbers up, waits a second then repeats all the numbers again.
I'm quite new to coding so i don't know how to fix this.
If someone could tell me how to do it, it would be greatly appreciated.

There are multiple issues in your code, although you are using setInterval(), since you have a while loop inside it, the complete loop will be executed every 1 second.
Instead you need to have the setInterval() callback use an if statement to check whether to print the value or not like
var count = 1;
var interval = setInterval(function write_numbers() {
if (count <= 1218) {
document.body.appendChild(document.createTextNode(count));
document.body.appendChild(document.createElement('br'));
count++;
} else {
clearInterval(interval);
}
}, 1000)

The below script should do the trick for you:
<script>
var count = 1;
var brk = "<br>";
var myVar = setInterval(function(){ myTimer() }, 1000); // This should be a global variable for clearInterval to access it.
function myTimer() {
document.write(count + brk);
count++;
if(count > 1218){
myStopFunction();
}
}
function myStopFunction() {
clearInterval(myVar);
}
</script>

two issues
1) If you are using setInterval then you must clear the interval as well otherwise it will be an infinite loop
2) use if rather than while so that number is printed one by one.
try this
var count = 1;
var interval1= setInterval(function write_numbers(){
var brk = "<br>"
if (count < 1218)
{
document.write(count + brk);
count++;
}
else
{
count = 1;
clearInterval(interval1);
}
},1000);

First, you should define count outside setInterval. Defining inside will reset it every time.
Second, while (count < 1218){} should be a conditional statement. I have considered if(count>= 1218) as termination condition.
Third, when even you use setInterval, remember to use clearInterval as well.
Code
var count = 1;
var interval = setInterval(function write_numbers() {
var brk = "<br>"
document.write(count + brk);
count++;
if (count >= 10) {
window.clearInterval(interval);
}
}, 1000)

Try this code man , only one change from your code.
count variable declare out side of the setInterval function
<script type="text/javascript">
var count = 1;
setInterval(function write_numbers(){
var brk = "<br>"
if (count < 1218)
{
document.write(count + brk);
count++;
}
},1000);
</script>

Javascript setTimeout not working in a for-loop

I have to change the source of an image every second. I have a for loop in which a call a function that has a timeout. I read that here, on stackOverflow, but it doesn't work. Can please someone tell me what can I fix to make it work? I've been struggling with this for much more that I'd like to admit. Thanks.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<script type="text/javascript">
function changeImage(k) {
setTimeout(function(){
document.getElementById("img").src = k + ".png"; alert(k );}, 1000);
}
function test() {
for (var k = 1; k <= 3; k++) {
changeImage(k);
}
}
</script>
</head>
<body>
<div id="main_img">
<img id="img" src="http://placehold.it/110x110">
</div>
<input type="button" style="width: 200px" onclick="test()" />
</body>

In your code, you set all the timeouts at once. So if you set them all one second from now they all fire one second from now.
You are already passing in the index k so just multiply the time parameter by k.
setTimeout(function(){
document.getElementById("img").src = k + ".png";
alert(k);
}, k * 1000);
// ^ added

The problem is that you are creating instances of a timer milliseconds apart. One second later, they all execute milliseconds apart as well. What you need is to execute them at a set interval apart from each other.
You can use a timer using setInterval, which executes the provided function at a given interval. Don't forget to kill-off the timer though, otherwise it will run forever.
Minor optimizations
You can cache the element in a variable so you won't be hitting the DOM that frequently.
Also, I'd avoid the alert(). If you are debugging, use breakpoints in the debugger. If you really want it to be "alert-like", then use console.log and watch the console.
An advantage of setInterval over a recursive setTimeout is that you will not be spawning multiple timers per iteration, but instead, just one timer.
And here's the proposed solution:
var k = 0;
var image = document.getElementById("img");
var interval = setInterval(function() {
// Increment or clear when finished. Otherwise, you'll leave the timer running.
if(k++ < 3) clearInterval(interval);
image.src = k + ".png";
// Execute block every 1000ms (1 second)
},1000);

Instead of using loop, you can do it like this:
var k = 0;
var int = setInterval(function() {
if (k <= 3) k++;
else { clearInterval(int); }
document.getElementById("img").src = k + ".png";
alert(k);
}, 1000);

My advice is to use console.log() or alert() to help you debug - it'll make it a LOT more obvious what's going on. For instance, if you put a console.log in your test or setTimeout functions, you'd see that all three images were getting added at the same time.
What I'd recommend is to declare your "nextImage" function, then define your setTimeout within that function. That way it'll call itself every second.
Another tip: I assume you want the three images to loop forever, so I added an often used trick with the modulus operator (%) to accomplish this.
Have a look:
Working demo: http://jsfiddle.net/franksvalli/PL63J/2/
(function(){
var numImages = 3, // total count of images
curImage = 1, // start with image 1
$image = document.getElementById("img"),
imageBase = "http://placehold.it/110x11";
function nextImage() {
$image.src = imageBase + curImage;
// increment by one, but loop back to 1 if the count exceeds numImages
curImage = (curImage % numImages) + 1;
// execute nextImage again in roughly 1 second
window.setTimeout(nextImage, 1000);
}
// initializer. Hook this into a click event if you need to
nextImage();
})();
As other folks have said, you probably want to use setInterval, which you can do with some tweaks:
(function(){
var numImages = 3, // total count of images
curImage = 1, // start with image 1
$image = document.getElementById("img"),
imageBase = "http://placehold.it/110x11";
function nextImage() {
$image.src = imageBase + curImage;
// increment by one, but loop back to 1 if the count exceeds numImages
curImage = (curImage % numImages) + 1;
}
// initializer. Hook this into a click event if you need to
nextImage(); // call function immediately without delay
window.setInterval(nextImage, 1000);
})();

The problem
setTimeout doesn't stop the program execution but only sets up an event for a callback in 1 second. What that means is that if you setup three setTimeout's inside your for loop, they will execute simultaneously after 1 second.
A solution
Instead of using a for loop, you can use a delayed recursion.
function changeImage(imageIndex) {
document.getElementById("img").src = imageIndex + ".png";
alert(imageIndex);
}
function myLoop( imageIndex ) {
if( imageIndex >= 3 ) return;
changeImage( imageIndex );
setTimeut( function() { myLoop(imageIndex + 1) }, 1000 );
}
setTimeut( function() { myLoop(0) }, 1000 );
Another solution using setInterval
var interval = null;
var imageIndex = 0;
function changeImage() {
document.getElementById("img").src = imageIndex + ".png";
alert(imageIndex);
imageIndex++;
if( imageIndex === 3 ) clearInterval( interval );
}
interval = setInterval( changeImage , 1000);
Using different delays
function changeImage(imageIndex) {
document.getElementById("img").src = imageIndex + ".png";
alert(imageIndex);
}
for( var i=0; i < 3; i++) {
setTimeout( changeImage.bind(window, i), i * 1000 );
}
A groovy one liner( please don't use this, ever! )
(function f(i) { setTimeout( changeImage(i) || f.bind(window, i = (i++)%3), 1000); })(0)

WHY IT DOESN'T WORK?
Because Javascript always passes variables by reference. When your code is waiting on the queue, the variables have already changed.
MY SOLUTION:
Create an array and push whatever codes you want to execute in order of appearance (Place the real value of the variables directly) e.g.:
var launcher = [];
launcher.push('alert("First line of code with variable '+ x +'")');
launcher.push('alert("Second line of code with variable '+ y +'")');
launcher.push('alert("Third line of code with variable '+ z +'")');
Use setInterval instead of setTimeout to execute the codes (You can even change the delay period dynamically) e.g.
var loop = launcher.length;
var i = 0;
var i1 = setInterval(function(){
eval(launcher[count]);
count++;
if(i >= loop) {
clearInterval(i1);
}
}, 20);

How to create pause or delay in FOR loop?

I am working on a website, where I need to create a pause or delay.
So please tell me How to create pause or delay in for loop in javascript or jQuery
This is a test example
var s = document.getElementById("div1");
for (i = 0; i < 10; i++) {
s.innerHTML = s.innerHTML + i.toString();
//create a pause of 2 seconds.
}

You can't use a delay in the function, because then the change that you do to the element would not show up until you exit the function.
Use the setTimeout to run pieces of code at a later time:
var s = document.getElementById("div1");
for (i = 0; i < 10; i++) {
// create a closure to preserve the value of "i"
(function(i){
window.setTimeout(function(){
s.innerHTML = s.innerHTML + i.toString();
}, i * 2000);
}(i));
}

var wonderfulFunction = function(i) {
var s = document.getElementById("div1"); //you could pass this element as a parameter as well
i = i || 0;
if(i < 10) {
s.innerHTML = s.innerHTML + i.toString();
i++;
//create a pause of 2 seconds.
setTimeout(function() { wonderfulFunction(i) }, 2000);
}
}
//first call
wonderfulFunction(); //or wonderfulFunction(0);
You can't pause javascript code, the whole language is made to work with events, the solution I provided let's you execute the function with some delay, but the execution never stops.

I tried all one, but I think this code is better one, it is very simple code.
var s = document.getElementById("div1");
var i = 0;
setInterval(function () {s.innerHTML = s.innerHTML + i.toString(); i++;}, 2000);

if you want to create pause or delay in FOR loop,the only real method is
while (true) {
if( new Date()-startTime >= 2000) {
break;
}
}
the startTime is the time before you run the while
but this method will cause the browsers become very slow

It is impossible to directly pause a Javascript function within a for loop then later resume at that point.

This is how you should do it
var i = 0;
setTimeout(function() {
s.innerHTML = s.innerHTML + i.toString();
i++;
},2000);

The following code is an example of pseudo-multithreading that you can do in JS, it's roughly an example of how you can delay each iteration of a loop:
var counter = 0;
// A single iteration of your loop
// log the current value of counter as an example
// then wait before doing the next iteration
function printCounter() {
console.log(counter);
counter++;
if (counter < 10)
setTimeout(printCounter, 1000);
}
// Start the loop
printCounter();

While several of the other answers would work, I find the code to be less elegant. The Frame.js library was designed to solve this problem exactly. Using Frame you could do it like this:
var s = document.getElementById("div1");
for (i = 0; i < 10; i++) {
Frame(2000, function(callback){ // each iteration would pause by 2 secs
s.innerHTML = s.innerHTML + i.toString();
callback();
});
}
Frame.start();
In this case, it is nearly the same as the examples that use setTimeout, but Frame offers a lot of advantages, especially if the you are trying to do multiple or nested timeouts, or have a larger JS application that the timeouts need to work within.

I am executing a function where I need access to the outside object properties. So, the closure in Guffa solution doesn't work for me. I found a variation of nicosantangelo solution by simply wrapping the setTimeout in an if statement so it doesn't run forever.
var i = 0;
function test(){
rootObj.arrayOfObj[i].someFunction();
i++;
if( i < rootObj.arrayOfObj.length ){
setTimeout(test, 50 ); //50ms delay
}
}
test();

The way I found was to simply use setInterval() to loop instead. Here's my code example :
var i = 0;
var inte = setInterval(() => {
doSomething();
if (i == 9) clearInterval(inte);
i++;
}, 1000);
function doSomething() {
console.log(i);
};
This loops from 0 to 9 waiting 1 second in between each iteration.
Output :
0 1 2 3 4 5 6 7 8 9

It is not possible to pause a loop. However you can delay the execution of code fragments with the setTimeout() function. It would not make a lot of sense to pause the entire execution anyway.

I am using while loop and check the pause variable to check the user pause/resume the code.
var pause = false;
(async () => {
for (let index = 0; index < 1000; index++) {
while (pause) {
await new Promise((res) => setTimeout(res, 1000));
console.log("waiting");
}
await new Promise((res) => setTimeout(res, 1000));
console.log(index);
}
})();
const pausefunc = async () => {
pause = true;
};
const playfunc = () => {
pause = false;
};
<button onclick="playfunc()">Play</button>
<button onclick="pausefunc()">Pause</button>

I used a do...while loop to put a delay in my code for a modal dialog that was closing too quickly.
your stuff....
var tNow = Date.now();
var dateDiff = 0;
do {
dateDiff = Date.now() - tNow;
} while (dateDiff < 1000); //milliseconds - 2000 = 2 seconds
your stuff....