JavaScript - Setinterval Question

How would you use setInterval so that theres a delay each time javascript runs through a certain loop?

In my mouseClick function I have a setInterval which call cursor function. Unfortunately it's not working. Below is my code:

Code:

var canvas;
var ctx;
var cursor_width = 1;
var cursor_height = 16;
var wait_time = 500;
var repeat_time = 1000;
var height = 22;
var textbox = new Array();
var repeat;

function Class(__proto__) {
    var Class = __proto__.hasOwnProperty("constructor") ? __proto__.constructor : (__proto__.constructor = function () {});
    Class.prototype = __proto__;
    return Class;
}

Class.prototype = Function.prototype;


function init(CanvasName) {
	canvas = document.getElementById(CanvasName);
	ctx = canvas.getContext("2d");
}


//============================================= Textfield =============================================

textfield = new Class({
		constructor: function (x, y, w) {
			this.x = x;
			this.y = y;
			this.w = w;
			this.text = new Array();
			var coordinates = new Array();
			coordinates.x = x;
			coordinates.y = y;
			coordinates.w = w;
			textbox.push(coordinates);
			
		},
		
		display: function () {
			ctx.beginPath();
			ctx.rect(this.x, this.y, this.w, height);
			ctx.closePath();
			ctx.stroke();
			
			canvas.addEventListener("mousedown", this.mouseClick, false);
		},
		
		cursor : function () {
			this.cursor_posX = this.x + 3;
			this.cursor_posY = this.y + 3;
			ctx.beginPath();
			ctx.strokeStyle = "black";
			ctx.rect(this.cursor_posX, this.cursor_posY, cursor_width, cursor_height);
			ctx.closePath();
			ctx.stroke();
			setTimeout(this.animateCursor, wait_time);
		},
		
		animateCursor :function () {
			ctx.strokeStyle = "white";
			ctx.stroke();
		},
		
		mouseClick: function (evt) {

			var mouse_posX = evt.clientX - canvas.offsetLeft;
			var mouse_posY = evt.clientY - canvas.offsetTop;
			var self = this;
			// if mouse coordination is within a texfield display cursor
			for (child in textbox){
				if((mouse_posX > textbox[child].x && mouse_posX < (textbox[child].x + textbox[child].w)) && (mouse_posY > textbox[child].y && mouse_posY < (textbox[child].y + height))) { 
					repeat = setInterval(this.cursor, repeat_time);
					canvas.addEventListener("keypress", this.displayText, false);
			
					break;
				}
				else
				{
					clearInterval(repeat);
					canvas.removeEventListener("keypress", this.displayText, false);
				}
			}	
		}
});

I tried the following code as well but I received a message telling me it's not a function

Code:

repeat = setInterval("this.cursor()", repeat_time);

Can anyone help me please

I have this:

function doThese(id){

clearInterval(interval);

doThis(id);

var interval = function(){
setInterval("doThis('"+id+"')", 2000);
}

interval();
doThisToo(id);
alsoDoThis(id);
}

Everything works fine together. However when I run the doThese() function a second time(with different id), the interval keeps using the id of the first run.

Thought clearinterval would fix that.. it doesn't. Any suggestions?

Thx in advance.

i have found a very simple ajaxexample on the internet, when this works i can adept it to my site, but it doesn't work :-( anybody sees why?
Code:

<div align="center" id="timeval">--:--:--</div> 
                                                <button id="stop">Stop</button> 
                                                  
                                                                <script src="jquery.js"></script> 
<script> 
$(document).ready(function() 
{ 
   //ajaxTime.php is called every second to get time from server 
   var refreshId = setInterval(function() 
   { 
     $('#timeval').load('ajaxTime.php?randval='+ Math.random()); 
   }, 1000); 

   //stop the clock when this button is clicked 
   $("#stop").click(function() 
   { 
     clearInterval(refreshId); 
   }); 
}); 
</script> 

and the phpscript: 

ajaxtime.php 

<?php 
   echo date("g:i:s A"); 
?>

Hello,

I'm having trouble with some scripts conflicting and interrupting my animation. I have a small website build around Joomla and I do my own modules and components.. I've made a simple browser game that uses Javascript's setInterval to highlight some elements. A few days ago I decided to add some advertising banners to cover the server costs but those banners are using Javascript and are interrupting my "game"...

Is there a way to stop that from happening ?

The script flow goes like this...

Step 1.
An XMLHttpRequest is being made and the server returns X numbers of elements out of Y total elements that need to get highlighted.

Step 2.
The elements default state is "blank" then a loop goes through the Y elements and sets a className of "highlight" on the elements that need to get highlighted.

Step 3.
The setInterval is being called and executes the code that highlights the X elements on every interval.

Code:

mytimer = setInterval ( animation, 500 );

The animation variable holds a function that changes the elements with class "highlight" to "highlighted".

Some pseudo-code:
Code:

// After all the AJAX requests and more doodle codes...
while(i < num_arr.length) { // num_arr holds the X numbers to get marked as highlight
     document.getElementsByTagName('td').item(X).setAttribute('name', 'highlight');
     i++;
}

mytimer = setInterval ( animation, 500 );

var animation = function() {
     document.getElementsByTagName('td').item(X).className = 'highlighted';
     // There is an "if" check to kill the setInterval if no more Xs are found
     clearInterval(mytimer);
}

* The above code is just a short example of the actual script *

Any help would be much appreciated..

Thank you.

Hello. I'm trying to get a script (and an html page, I guess) to run constantly, and I'm pretty sure I should be using setInterval() to do this. But I'm not familiar enough with Javascript to know what I'm doing wrong, or what I need to fix. This is the code...

Code:

<html>
	<head>
		<script type="text/javascript" src="wz_jsgraphics.js"></script>
		<script type="text/javascript">
		<!--			
		function initialize_field() {
			var jg = new jsGraphics();
			var pixel_spacer = 10;
			var field_length = 1000;
			var field_width = 600;
			jg.drawRect(pixel_spacer,pixel_spacer,field_length,field_width);
			//...
			return jg
			}
			
		function main() {
			our_field = initialize_field();
			dateobj = new Date();
			current_time = dateobj.getMilliseconds();
			our_field.drawString("Hello world!",current_time,500);
			our_field.paint();
			}
			
		
		-->
		</script>
	</head>
	
	<body onload="main(); setInterval('main()', 250 )">
	</body>
</html>

If I understand setInterval() correctly, this should cause the page to run the main() function every 250 seconds. And within main(), the "Hello world!" string is being drawn at some point between 0 and 1000 pixels, depending upon the number of milliseconds, so it should essentially be scrolling across the screen. But I can only get it to "scroll" if I hammer F5 to repeatedly load the page. How can I get the main() function to run repeatedly?

I tried calling main() from main(), but that did not work well...

Thanks for any suggestions you have!

thanks for your time - I am more of a hacker than a coder.

I have a webpage with a setinterval script I put together which reloads another page's php content into an iframe on the page. It works fine in IE, but doesnt work in FF or Chrome. (I dont want to use a refresh meta though that seems to work in IE & Chrome but not FF.)

Here's the script snippet I wrote:
Code:

<script>
window.setInterval("reloadIFrame();", 5000);
function reloadIFrame() {
 document.frames["chat"].location.reload();
}
</script>
<iframe id="chat" src="../chat/buffer.php" width="100%" height="200"></iframe>

on the page's first load, all the info is there in the iframe, but except for IE, updates do not show (the reloads dont seem to occur).

I have a javascript that precedes this script containing a setTimeout, but never had issues with it. I can post the entire page code, if needed...

thanks again.
HWL

I found a little chat script online and I wanted to check it out. When I integrated it into a page I created, for some reason this will not work correctly

<body onload="setInterval('chat.update()', 1000)">

I tested it with two different browswers open

Lets say on two different browser windows you have user1 and user2

if user1 types 'Hello'
it will not show up on user2 window
but if user2 types 'Hi'

then on user2 window it will say
user1 says Hello
user2 says Hi

so basically for user1 to see what user2 has wrote, user1 has to type something first and send it to see what user2 said.

hope you understand, if you would like I could post up the code.

Hi all,
I'm new to Javascript, and having an issue with getInterval. For my programming languages class we have to create a simulation of waves breaking on a shore from above. I've decided to use a canvas object and Javascript for this animation, but am getting stuck on refreshing the frames. Here is the code I have so far:

Code:

var shoreline = new Array();
var waves = new Array();
var canWidth = 600;
var canHeight = 400;
var waveNum = 0;
var count = 0;

function wave() {
	setupShore();
	var canvas = document.getElementById("canvas");
	canvas.setAttribute("width",canWidth);
	canvas.setAttribute("height",canHeight);
	var ctx = canvas.getContext("2d");
	createWave();
	setInterval(update(ctx), 1000);
}
	
function update(ctx) {
	if(waves.length != 0) {
		drawWater(ctx);
		drawShore(ctx);
		drawWaves(ctx);
		updateWaves();	
	}
}

function drawElement(ctx, x, y, width, height, fillcolor) {
	ctx.fillStyle = fillcolor;
	ctx.fillRect(x, y, width, height);
}

function setupShore() {
	for(var i = 0; i <= canWidth/5; i++) {
		shoreline[i] = Math.round(canHeight/5); // + Math.floor(Math.random()*101);
	}
}

function createWave() {
	/*	Wave array setup:
		[ [waveID1, [node1, node2, ..., nodeN]], 
		[waveID2, [node1, node2, ..., nodeN] ] */
	waves.push([waveNum, []]);
	for(var c = 0; c <= canWidth/5; c++){
		waves[waves.length-1][1].push(canHeight);
	}
	waveNum = waveNum + 1;
}

function destroyWave() {
	waves.shift();
}

function drawWater(ctx) {
	drawElement(ctx, 0, 0, canWidth, canHeight, "#336699");
}

function drawShore(ctx) {
	for(var s = 0; s <= shoreline.length; s++) {
		drawElement(ctx, s*5, 0, 5, shoreline[s], "#FFCC00");
	}
}

function updateWaves() {
	for(var u = 0; u < waves.length; u++) {
		var limit = waves[u][1].length;
		for(var v = 0; v < limit; v++){
			var temp = waves[u][1][v]-5;
			waves[u][1][v] = temp;
			if(waves[u][1][v] <= shoreline[v]){
				destroyWave();
			}
		}
	}
}

function drawWaves(ctx) {
	for(var w = 0; w < waves.length; w++) {
		for(var n = 0; n <= waves[w][1].length; n++){
			y = waves[w][1][n];
			drawElement(ctx, n*5, y, 5, 5, "Purple");
		}
	}
}

As you can see, the idea is that each 5-pixel wide node of the shore and wave are stored in arrays so that the position of each node can differ. The wave() function initializes all the required data, and then calls setInterval on update(). The function update() draws the water, shore, and wave, and then updates the wave position node-by-node. Ideally, setInterval would cause this to happen repeatedly, so that the wave would appear to move closer to the shore every 1000ms.

However, this is not the case. It appears as though setInterval is working for one pass of update(), but fails after the first pass. You can tell that this is happening because the wave appears at its starting position, but does not continue to move.

Any idea why this is happening? I read somewhere that setInterval can be broken by one-time functions, but I'm not sure.

If you'd like to see what it's currently doing in a browser, I've hosted it here.

Once I've got this animating properly I can continue my project, but I've hit a roadblock. Thanks in advance for your help, I'm really stuck.

Marcus

Hi, all. I am very new to Javascript (and coding generally); the code below is part of my first project. I teach, and just built a flash card / timed-drill site for my students which has a number of setIntervals going on as a central part of its timed functionality.

I ran into a problem when trying to create controls that would allow adjustments in the drill timing within the same page. The running setIntervals simply need to be killed when a variable is changed through the user form input, but I cannot seem to do this through any means known to me. I've tried about 15 different approaches and none of them work. Here is one function in my code that runs a setInterval and refuses to be killed by any external stimuli (like, say, a specific killerVariable value):

Code:

function countdownTimer()
    {
    var countdown=timeLimit/1000;
    var countdownString=countdown+'';
    document.getElementById("countdownTimerArea").innerHTML = countdownString;
    var killCountdown=setInterval(function()    {
                                                countdownString=(countdown-1)+'';
                                                document.getElementById("countdownTimerArea").innerHTML = countdownString;
                                                countdown--;
                                                if (countdown==0)
                                                    {
                                                    clearInterval(killCountdown);
                                                    }
                                                },1000);
    }

The clearInterval shown in the code *does* work correctly. However, if I try to set up another conditional, killerVariable-value-driven clearInterval in this function (or even change the above to if (countdown==0 || killerVariable==1), it does not stop the setInterval when killerVariable changes.

In the end, because I needed this to go online quickly, I "solved" this problem by simply creating a few different versions of the page with hard-coded variable values and having the form control buttons take the user to those pages rather than trying to stop and restart the timed processes within the same instance of the script. However, this was a real kludge of a solution, and I am still very curious as to what I could have done to actually make this work. Is there anything I could have done short of totally rewriting the function as a loop with setTimeout?

Alternately-- and this *does* seem incredibly basic, but I can't get an answer no matter how I phrase my Google and CF queries-- is there some way to hard-kill a currently running function via another function in Javascript? I think that would have solved my problems.

If you try some codes and then catch exception, it should catch the exception when there is. However, if there is a setInterval method in the try clause, then the exception cannot be caught... why???

the following works ( a usual method is invoked in the try clause):
Code:

<script language="javascript" type="text/javascript">
function invoke()
{   var i=0;    
    return i.x.y;
}

try
{
      alert(invoke());     
}  
catch(ex){ alert(ex); } //Any Exception will be caught.
</script>

if the highlighted line is changed as below (using setInterval method), then it fails...
Code:

<script language="javascript" type="text/javascript">
function invoke()
{   var i=0;    
    return i.x.y;
}

try
{
      setInterval(alert('invoke())',1000);     
}  
catch(ex){ alert(ex); } //The Exception will NOT be caught.
</script>

any idea? thx in advance

This question probably has an obvious answer, but I'm an ActionScript guy and not a JS guy. I was just playing around with getting intervals to work with JS and ran into this weirdness.

The page in question is he http://erikphansen.com/intervaltest.html

It will remove the text on the page and add new text every 500ms. Click anywhere to stop it. It works fine in Safari. In Firefox it runs once, then seems to cause Firefox to just hang. The spinner just runs on the tab and nothing gets updated. To make things more unusual, refreshing the page in Firefox doesn't do anything.

Here is the code:

Code:

theCounter = 0;

function writeText(arg)
{
	theCounter++
	document.write("<p>" + arg + " " + theCounter + "</p>")
}

function stopTheStuff()
{
	clearInterval(myInterval);
	alert("we stopped it");
}

// Two different ways of setting intervals have the same issue...
// ...and both work in Safari for Mac

// myInterval = setInterval("writeText('write this: ')", 500);
myInterval = setInterval(writeText, 500, "write this: ");

document.onclick = stopTheStuff;

Help show a newbie the way!

Thanks a lot,
Erik

I realize this is an overly simple question, but I'm rather horrible at javascript. What I'm doing is changing an img src and having it loop through images. I want it to only start looping when I click and than stop if I click again.


It loops through when I click once, but when I click again it starts changing its rate of image switching. Starts off switching at 1000 milliseconds than upon clicking again it switches through two images quickly and than slows again.

Code:

var myImage = document.getElementById("mainImage");

var imageArray=["1.jpg","2.jpg","3.jpg","4.jpg" ];

var imageIndex=0;

What I assume is the trouble causing function:

Code:

function changeImage(){
	myImage.setAttribute("src", imageArray[imageIndex]);
	imageIndex++;
	if(imageIndex >= imageArray.length) {
		imageIndex=0;
	}
}

How the trouble function is being called:
Code:

var imgSwtch=0;

myImage.onclick= function(){
		if(imgSwtch==0){
			var intervalHandle = setInterval(changeImage,1000);
			imgSwtch=1;
			console.log("start");
		}
		else{
			clearInterval(intervalHandle);
			imgSwtch=0;
			console.log("stop");
		}
		
};

Hi. I'm working on a script that picks out a random entry in an array every 10seconds and show it to the user (using document.write). So far I've got the "Randomizer" to work like this:

Code:

function random(){
	var nummer = Math.floor(Math.random()* tekst.length);
	return nummer;
}

var tekst = new Array("Different", "Values");

and showing it like this:

Code:

document.write(tekst[random()]);

Now, I've tried my best to implement setInterval() to give me a new random number every 10seconds, but so far without any luck...

I appreciate all help!

Thx in advance.

Hi there!
I'm trying to load up an array of images in HTML5, which will mimic a "video".
I've put together code for creating an array of images, which will be drawn by the draw() function, but I'm struggling to find the best way to achieve a setInterval ie make the "video" of images run at 30 fps.

At present, when I click the "Draw" button, the images load up, one after the other, just as in a video, but I can't seem to control this loading up speed.
Can anyone help? I'm sure I'm very close to a solution!
Here is my code:
Code:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<!--

  Created using /
  Source can be edited via /odexi/edit

-->
<head>
<title>Sandbox</title>
<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
<style type="text/css" media="screen">
body { background-color: #000; font: 16px Helvetica, Arial; color: #fff; }
</style>
</head>
<body>
  <input type="button" id="drawButton" value="draw" />
  <br/>
  
  <canvas id="canvas" width="1000px" height="800px">

  </canvas>
<script>
function init(){ 
var fps = 1000; // frames / second
    const timeInterval = 1000 / fps; // milliseconds  
  setInterval(draw,timeInterval);
  draw();
}
    function draw() { 
	//var fps = 30; // frames / second
    //const timeInterval = 1000 / fps; // milliseconds
      var ctx = document.getElementById('canvas').getContext('2d'), 
          img, i, image_array = [10]; 
 
      image_array.push("track1.png"); 
      image_array.push("track2.png");
      image_array.push("track3.png"); 
	  image_array.push("track4.png");
	  image_array.push("track5.png");
	  image_array.push("track6.png");
	  image_array.push("track7.png");
	  image_array.push("track8.png");
	  image_array.push("track9.png");
	  image_array.push("track10.png");
      // ... 
 
      for (i = 0; i < image_array.length; i++) { 
        img = new Image(); 
        img.src = image_array[i]; 
        img.onload = (function(img, i){ 
          return function () {
			//setInterval(draw, timeInterval);
            ctx.drawImage(img,0,0); 
          } 
        })(img, i); 
      } 
    } 

window.onload = function () {
  document.getElementById('drawButton').onclick = function () {
    draw();
  };
};
</script>
</body>
</html>