Develop Reference

How to use setInterval to trigger a function so that I can stop it at some point?

So from what I have understood, setInterval() is used to call a function on repeat on regular intervals.
So basically it is a loop that executes a function forever periodically.
I am confused as to if I had to stop this execution at one point what would be the way to do it
for eg I am trying to print the message "hey" 3 times after 1 second each, but somehow it is printing it 3 times every second and is going on forever.
What can I do to stop it after a set number of times.
This is the code that I've been trying
var i = 3;
function message() {
console.log("hey");
}
while(i > 0) {
setInterval(message, 1000);
i = i - 1;
}

Your code is executing the setInterval thrice in the while loop, which is not needed.
Actually, setInterval does not work as a function call but actually registers a function to be called at some interval.
The setInterval() method will continue calling the function until clearInterval() i.e it is deregistered or the process is killed.
It should work like this
var i = 3;
var interval = setInterval(message, 1000);
function message() {
if (i === 0) {
clearInterval(interval);
}
console.log("hey");
i = i - 1;
}

To clear a setInterval, use global clearInterval method.
Example:
var timerId = setInterval(func, 500);
.... some code here....
clearInterval(timerId);

What can I do to stop it after a set number of times.
usually you don't use setInterval() for this, you use setTimeout().
Something like
var counter = 0;
function message() {
console.log("hey");
// we trigger the function again after a second, if not already done 3 times
if (counter < 3) {
setTimeout(message, 1000);
}
counter++;
}
// initial startup after a second, could be faster too
setTimeout(message, 1000);

The setInterval function calls the function indefinitely, whereas setTimeout calls the function once only.
Simply use clearInterval once the count runs out.
var i = 3;
function message(){
console.log("hey");
if (--i < 0) {
clearInterval(tmr);
}
}
var tmr = setInterval(message, 1000);

you have to assign that setInterval to a javascript variable to name it what for this setInterval, like this
var messageLog = setInterval(message, 1000);
After, in setInterval message function add this condition to clear the inverval whenever you want to clear.
function message(){
if(i>3) {
clearInterval(messageLog); // clearInterval is a javascript function to clear Intervals.
return null;
}
console.log("hey");
}

You can retrieve the timer when creating and clear it if needed.
var i=3;
var timer = setInterval(message,1000);
function message(){
console.log("hey");
i—-;
if(i==0)
clearInterval(timer)
}

a beginner here too,look for clearInterval method ...

setInterval call to function with other arg

I have a function called "showCustomer" that get number between 1-5 and return something.
I want to use setInterval, to run this function every 5 second but with another number.
Its not working, i don't understand why its not working to me. here is the code.
setInterval(function () {
var i = 1;
showCustomer(i);
i++;
}, 5000);

Just move the declaration of variable i before the setInterval() call:
var i = 1;
setInterval(function () {
showCustomer(i);
i++;
}, 5000);
The anonymous function you've set as a callback for setInterval gets called every 5 seconds in your code. In every call, you're setting i to 1 which resets it every time.
Moving i outside the setInterval callback makes it persist the the current value.

Every time you use var, you redeclare the value of that variable. So you only should declare the counter one time.
Every time that the browser calls the callback showCustomer the if statement evaluates if the browser should make a new call.
clearInvertal() it's the method to stop the setInterval() method.
var id = 1;
var show5times = window.setInterval(showCustomer, 5000);
function showCustomer() {
alert(id);
id++;
if(id > 5) {
window.clearInterval(show5times);
}
}

Set Value of Variable on first instance of function running

For example I have a variable which should increment every time the function is run. I want the variable to initially be given the value of 0, but then increase by 1 every time the function is called. I do not want to give the variable global scope, however obviously if I declare it within the function it is going to be reset to 0 every time it is called.
Is there a simple and efficient way to to do this in Javascript?
My Javascript:
function myFunction(){
var i=0;
//Body of function
i++;
}

You can set the value on the function object itself, like this
function myFunction() {
myFunction.i = myFunction.i || 0;
myFunction.i++;
}
Alternatively, you can use closure, like this
var myFunction = (function () {
var i = 0;
return function () {
// `myFunction` will be this function only and it increments the
// `i` from the enclosed function.
i++;
}
})();

Change millisec for window.setInterval function

I used window.setInterval function. this function includes 3 arguments :
setInterval(code,millisec,lang)
I used that like this:
var counter = 1;
window.setInterval(function() {}, 1000 * ++counter);
but when first time set timer (second argument), is not changed and that act Like below code:
window.setInterval(function() {}, 1000);
please write correct code for change timer

Use window.setTimeout instead.
var delay = 1000;
function myTimer() {
// do whatever
window.setTimeout(myTimer, delay);
}
window.setTimeout(myTimer, delay);
You can manipulate delay in the body of your function.

Your problem is that javascript first execute '1000 * ++counter' once and then do not update the time interval.
You should try to use a timeout instead: https://developer.mozilla.org/en/DOM/window.setTimeout
And create a new time out with the new value every time your time out function is called.

Sounds like what you're after is not setInterval but rather setTimeout in a loop:
var counter = 1;
for (var i = 1; i <= 3; i++) {
window.setTimeout(function() {
alert("#" + counter);
counter++;
}, i * 1000);
}
This will execute three different "timers" one after the other.
Live test case: http://jsfiddle.net/86DRd/

jQuery increment setInverval()

Uh..... I have no idea why this simple code snippet isn't working:
function increment() {
var count = 0;
alert(count++);
}
setInterval(increment, 1000); // test
it should display the next number repeatedly, right? It just displays "0". Help appreciated. Thanks.

count needs to be a global variable. You are referencing your local variable count. Every time the function executes, it gets set to 0. You are using count++, so the value passed to alert is 0, and the incremented value is never used.
To fix this, move the declaration of count outside of your function (as per answer by Tim):
var count = 0;
function increment() {
alert(count++);
}
setInterval(increment, 1000); // test

var count = 0;
function increment() {
   alert(count++);
   }
 setInterval(increment, 1000); // test