global variables in js, how to avoid them - javascript

I have a change() function that uses a setInterval() to repeat an animation:
function change(){
interval = setInterval(c,300);
function c(){...}
c()
}
The c() function does the work.
I also have a stop() function that stops all the animation and restore the initial situation:
function stop(){
clearInterval(interval);
...
};
I've read that is better use the var keyword instead declaring a global variable. But I cannot get access from the stop() function to interval if I do so. Declaring interval outside the change() function also gives me a problem.
ok i'm trying the last solution proposed by Ben Aston. Here the code:
function Animator() {
var id;
return {
start: start,
stop: stop,
};
function start() {
id = requestAnimationFrame(go);
}
function stop() {
clearAnimationFrame(id);
}
function go() {
// increment the animation
for (var i=0;i<img.length;i++){
var num = randNum(0,img.length-1)
var btn = img[i].nextSibling.nextSibling.childNodes[1]
img[i].setAttribute("src",img_path[num].path);
$(btn).css({"background-color":img_path[num].color,"border":"4px solid"+img_path[num].color});
$(img[i]).animate({width: "-=80px", height: "-=80px"},'slow');
$(img[i]).animate({width: "+=80px", height: "+=80px"},'slow')}
id = requestAnimationFrame(go)
}
}
basically when the user press a button, the images start to change their width and height and their color.
this is the rest:
var animator = new Animator();
function stop(){ //fn related to the stop button
animator.stop()};
function change(){ //fn related to the start button
animator.start()}
I dont know how to use requestAnimationFrame properly, i'm studying it right now. but when i press the start button the images change just one time and then they stopped.
In the previous code i had a for loop that did the work:
function change(){
interval = setInterval(c,300);
function c(){
for (var i=0;i<img.length;i++){
var num = randNum(0,img.length-1)
var btn = img[i].nextSibling.nextSibling.childNodes[1]
img[i].setAttribute("src",img_path[num].path);
$(btn).css({"background-color":img_path[num].color,"border":"4px solid"+img_path[num].color});
$(img[i]).animate({width: "-=80px", height: "-=80px"},'slow');
$(img[i]).animate({width: "+=80px", height: "+=80px"},'slow')}}
c()}
I admit that i dont have quite clear how to implement the go func?
thanks
edit: now it works (i was working with another file :)) but i have problem with the stop button

You can use Closure as well, read the documentation here :
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures
With Closure you can define private and public function.

In raw JavaScript you could do the following:
Using ES5:
function Animator() {
var id;
return {
start: start,
stop: stop,
};
function start() {
id = requestAnimationFrame(go);
}
function stop() {
clearAnimationFrame(id);
}
function go() {
// increment the animation...
if(shouldContinue()) { // you define `shouldContinue`
id = requestAnimationFrame(go);
}
}
}
var animator = new Animator();
animator.start();
// ...
animator.stop()

hi using closures and with set interval things works properly:
var Button_Obj = function(){
var intervalID;
function start(){
return intervalID = setInterval(change,300) //change is the function that do the animation with a loop, i keep it private
};
function stop(){
clearInterval(intervalID)
};
return {start : start, stop : stop}
now in the global space i have only:
var btn_trigger = new Button_Obj();
and in the button tag i put:
<button style="border:1px solid #9dbbe4;" class="change-button" id="change-order" onclick="btn_trigger.start()" type="button">Start Moving</button>
now the global space is more clean, this implmentation works, with RequestAnimationFrame i have some problem, but i will try with it as well later

Related

Implement press and hold on a button

Thank you for the previous (deleted by moderator) explanation and the simple implementation but it does not work out for me. The 'holdit' function works but it is not is not steady probably because there is an 'onmouseup' in the 'holdit' function too, Even if I disable the onmouseup at the HTML button it's not very steady. Maybe it's better to use an addEventListener- onmousedown-interval function but again I don't know how to implement it in the simplest possible way. Here's the complete function that shows a pressed button and increases the timeSeconds var by one. For safety the var. number is within a limit.
Please help.
HTML:
<img id="but4" class="button" src= "//:0" onmousedown="timesecPlus();"onmouseup="timesecPlsUp();"/>
JAVASCRIPT:
function timesecPlus() {
var pmknop = document.getElementById('but5');
pmknop.src = secminBtndwn; //inline Base64 data: button image down (pressed)
timeSeconds = ((timeSeconds>wedstrijdperiode.seconden-6)?(timeSeconds):(++timeSeconds)); //You can ++ chase-back the timeseconds until 5 sec's from period start-time
displayTime( timeSeconds );
};
function timesecPlsUp() {
var pmknop = document.getElementById('but5');
pmknop.src = secminBtn; //inline Base64 data: button image up (normal)
};
// Things I tried:
//holdit(pmknop, function () { ++timeSeconds ; displayTime( timeSeconds );}, 2000, 2);
//pmknop = pmknop.addEventListener('mousedown', function() { interval = setInterval(timesecPlus (), 2000); });
function holdit(btn, action, start, speedup) {
var t;
var repeat = function () {
action();
t = setTimeout(repeat, start);
start = start / speedup;
}
btn.onmousedown = function() {
repeat();
}
btn.onmouseup = function () {
clearTimeout(t);
}
};
The holdit function is taking four variables. The first: btn, is the button id. This is used to determine the action performed whenever the mouse is clicked.
The second variable is a reference to a function. Its called a callback function, since you will be passing a function that will be Caaalleed whenever you call holdit.
The last two variables simply determine when and how long to delay the execution of the repetition and and by how much each repetition will speed up by.
var repeat = function () {
action();
t = setTimeout(repeat, start);
start = start / speedup;
}
Repeat is a recursive function that will be called after 'start' number of milliseconds and be repeated more frequently after each iteration.
Simple implementation:
var btn = document.getElementsByClassName('button')[0];
holdit(btn, function () { timeSeconds++ ; displayTime( timeSeconds );}, 1000, 2);
Implementation without holdit:
var btn = document.getElementsByClassName('button')[0];
var couterFunc, couter=0;
btn.addEventListener('mousedown',function(){couterFunc = setInterval(update,1000); update()})
btn.addEventListener('mouseup',function(){clearInterval(couterFunc)})
/* function that will fire when button press*/
function update(){console.log(++couter)};

Clearing setInterval() Issue

I have a setInterval on a function X that runs every 500ms. In this function X, I call another function Y that essentially binds an event on some divs. However, I would like to unbind these events the next time the function X is called (to start "fresh"). My code doesn't seem to work:
setInterval(this.board.updateBoard, 500); //called from another constructor
This then initiates the functions below:
Board.prototype.updateBoard = function() {
//I attempt to unbind ALL my divs
var divs = this.$el.find("div");
for(var i = 0; i < divs.length; i++) {
$(divs[i]).unbind(); //Apparently this doesn't work?
}
//...some code here...
//find appropriate $div's (multiple of them), and then calls this.beginWalking() below on each of those
//loop here
this.beginWalking($div, direction + "0", direction + "1");
//end of loop
}
//alternate between classes to give appearance of walking
Board.prototype.beginWalking = function ($div, dir0, dir1) {
return setInterval(function () {
if ($div.hasClass(dir0)) {
$div.removeClass(dir0);
$div.addClass(dir1);
} else {
$div.removeClass(dir1);
$div.addClass(dir0);
}
}.bind(this), 80);
};
Basically, updateBoard is called every 500ms. Each time it's called, beginWalking is called to set another interval on a div. The purpose of this other interval, which functions correctly, is to add and remove a class every 80ms. I just can't seem to unbind everything before the next updateBoard is called.
Any suggestions appreciated!
use clearInterval()
edit: $(selector).toggleClass(dir0) might also be helpful
// In other file, use a global (no var) if you need to read it from another file:
updaterGlobal = setInterval(this.board.updateBoard, 500);
// store interval references for clearing:
var updaterLocals = [];
Board.prototype.updateBoard = function() {
//I attempt to unbind ALL my divs
var divs = this.$el.find("div");
// Stop existing div timers:
while(updaterLocals.length > 0){
clearInterval(updaterLocals[0]);
updaterLocals.shift(); // remove the first timer
}
//...some code here...
//loop here to call the below on several $div's
this.beginWalking($div, direction + "0", direction + "1");
//end of loop
}
//alternate between classes to give appearance of walking
Board.prototype.beginWalking = function ($div, dir0, dir1) {
var interval = setInterval(function () {
if ($div.hasClass(dir0)) {
$div.removeClass(dir0);
$div.addClass(dir1);
} else {
$div.removeClass(dir1);
$div.addClass(dir0);
}
}.bind(this), 80);
// Save the timer:
updaterLocals.push(interval);
return;
};

Destroy previous setInterval

I want a function to set an Ajax and a reload timer. The code below doesn't destroy the previous function call timer, so each time I invoke it I get another timer. How can I destroy the previous timer?
function initNowPlayingMeta(station) {
$('#cancion').children().remove();
$('#cancion').load('sonando.php?emisora=' + station);
var prevNowPlaying = setInterval(function () {
$('#cancion').load('sonando.php?emisora=' + station);
}, 5000);
}
You need to store your timer reference somewhere outside of local scope (this essentially means declaring it with var outside of the function). Then, clear it with clearInterval:
var prevNowPlaying = null;
function initNowPlayingMeta(station) {
if(prevNowPlaying) {
clearInterval(prevNowPlaying);
}
$('#cancion').children().remove();
$('#cancion').load('sonando.php?emisora=' + station);
prevNowPlaying = setInterval(function () {
$('#cancion').load('sonando.php?emisora=' + station);
}, 5000);
}
clearInterval
clearInterval(prevNowPlaying);
you will also want to make the prevNowPlaying from previous calls in scope whereever you try to cancel
You need to explicitly clear the timer.
var prevNowPlaying;
function initNowPlayingMeta(station) {
$('#cancion').children().remove();
$('#cancion').load('sonando.php?emisora=' + station);
if (prevNowPlaying === undefined) clearInterval(prevNowPlaying);
prevNowPlaying = setInterval(function () {
$('#cancion').load('sonando.php?emisora=' + station);
}, 5000);
}
For people who only needs to destroy or stop a previous setInterval, not exactly what the question ask (jquery, song, etc)
const previousSetIntervalInstance = setInterval(myTimer, 1000);
//every 1 second update the time
function myTimer() {
  const date = new Date();
  document.getElementById("demo").innerHTML = date.toLocaleTimeString();
}
function myStopFunction() {
  clearInterval(previousSetIntervalInstance);
}
<h3>setInterval() and clearInterval() demo</h3>
<p id="demo"></p>
<button onclick="myStopFunction()">Stop the time</button>
Initial source: https://www.w3schools.com/jsref/met_win_clearinterval.asp
When you click on stop the time is not updated anymore
Basically, you need to store the setInterval output as global variable and pass it to clearInterval

setTimeout / clearTimeout problems

I try to make a page to go to the startpage after eg. 10sec of inactivity (user not clicking anywhere). I use jQuery for the rest but the set/clear in my test function are pure javascript.
In my frustation I ended up with something like this function that I hoped I could call on any click on the page. The timer starts fine, but is not reset on a click. If the function is called 5 times within the first 10 seconds, then 5 alerts will apear... no clearTimeout...
function endAndStartTimer() {
window.clearTimeout(timer);
var timer;
//var millisecBeforeRedirect = 10000;
timer = window.setTimeout(function(){alert('Hello!');},10000);
}
Any one got some lines of code that will do the trick?
- on any click stop, reset and start the timer.
- When timer hits eg. 10sec do something.
You need to declare timer outside the function. Otherwise, you get a brand new variable on each function invocation.
var timer;
function endAndStartTimer() {
window.clearTimeout(timer);
//var millisecBeforeRedirect = 10000;
timer = window.setTimeout(function(){alert('Hello!');},10000);
}
The problem is that the timer variable is local, and its value is lost after each function call.
You need to persist it, you can put it outside the function, or if you don't want to expose the variable as global, you can store it in a closure, e.g.:
var endAndStartTimer = (function () {
var timer; // variable persisted here
return function () {
window.clearTimeout(timer);
//var millisecBeforeRedirect = 10000;
timer = window.setTimeout(function(){alert('Hello!');},10000);
};
})();
That's because timer is a local variable to your function.
Try creating it outside of the function.
A way to use this in react:
class Timeout extends Component {
constructor(props){
super(props)
this.state = {
timeout: null
}
}
userTimeout(){
const { timeout } = this.state;
clearTimeout(timeout);
this.setState({
timeout: setTimeout(() => {this.callAPI()}, 250)
})
}
}
Helpful if you'd like to only call an API after the user has stopped typing for instance. The userTimeout function could be bound via onKeyUp to an input.
Not sure if this violates some good practice coding rule but I usually come out with this one:
if(typeof __t == 'undefined')
__t = 0;
clearTimeout(__t);
__t = setTimeout(callback, 1000);
This prevent the need to declare the timer out of the function.
EDIT: this also don't declare a new variable at each invocation, but always recycle the same.
Hope this helps.
Practical example Using Jquery for a dropdown menu !
On mouse over on #IconLoggedinUxExternal shows div#ExternalMenuLogin and set time out to hide the div#ExternalMenuLogin
On mouse over on div#ExternalMenuLogin it cancels the timeout.
On mouse out on div#ExternalMenuLogin it sets the timeout.
The point here is always to invoke clearTimeout before set the timeout, as so, avoiding double calls
var ExternalMenuLoginTO;
$('#IconLoggedinUxExternal').on('mouseover mouseenter', function () {
clearTimeout( ExternalMenuLoginTO )
$("#ExternalMenuLogin").show()
});
$('#IconLoggedinUxExternal').on('mouseleave mouseout', function () {
clearTimeout( ExternalMenuLoginTO )
ExternalMenuLoginTO = setTimeout(
function () {
$("#ExternalMenuLogin").hide()
}
,1000
);
$("#ExternalMenuLogin").show()
});
$('#ExternalMenuLogin').on('mouseover mouseenter', function () {
clearTimeout( ExternalMenuLoginTO )
});
$('#ExternalMenuLogin').on('mouseleave mouseout', function () {
clearTimeout( ExternalMenuLoginTO )
ExternalMenuLoginTO = setTimeout(
function () {
$("#ExternalMenuLogin").hide()
}
,500
);
});
This works well. It's a manager I've made to handle hold events. Has events for hold, and for when you let go.
function onUserHold(element, func, hold, clearfunc) {
//var holdTime = 0;
var holdTimeout;
element.addEventListener('mousedown', function(e) {
holdTimeout = setTimeout(function() {
func();
clearTimeout(holdTimeout);
holdTime = 0;
}, hold);
//alert('UU');
});
element.addEventListener('mouseup', clearTime);
element.addEventListener('mouseout', clearTime);
function clearTime() {
clearTimeout(holdTimeout);
holdTime = 0;
if(clearfunc) {
clearfunc();
}
}
}
The element parameter is the one which you hold. The func parameter fires when it holds for a number of milliseconds specified by the parameter hold. The clearfunc param is optional and if it is given, it will get fired if the user lets go or leaves the element. You can also do some work-arounds to get the features you want. Enjoy! :)
<!DOCTYPE html>
<html>
<body>
<h2>EJEMPLO CONOMETRO CANCELABLE</h2>
<button onclick="inicioStart()">INICIO</button>
<input type="text" id="demostracion">
<button onclick="finStop()">FIN</button>
<script>
let cuenta = 0;
let temporalTiempo;
let statusTime = false;
function cronometro() {
document.getElementById("demostracion").value = cuenta;
cuenta++;
temporalTiempo = setTimeout(cronometro, 500);
}
function inicioStart() {
if (!Boolean(statusTime)) {
statusTime = true;
cronometro();
}
}
function finStop() {
clearTimeout(temporalTiempo);
statusTime = false;
}
</script>
</body>
</html>

Resetting a setTimeout

I have the following:
window.setTimeout(function() {
window.location.href = 'file.php';
}, 115000);
How can I, via a .click function, reset the counter midway through the countdown?
You can store a reference to that timeout, and then call clearTimeout on that reference.
// in the example above, assign the result
var timeoutHandle = window.setTimeout(...);
// in your click function, call clearTimeout
window.clearTimeout(timeoutHandle);
// then call setTimeout again to reset the timer
timeoutHandle = window.setTimeout(...);
clearTimeout() and feed the reference of the setTimeout, which will be a number. Then re-invoke it:
var initial;
function invocation() {
alert('invoked')
initial = window.setTimeout(
function() {
document.body.style.backgroundColor = 'black'
}, 5000);
}
invocation();
document.body.onclick = function() {
alert('stopped')
clearTimeout( initial )
// re-invoke invocation()
}
In this example, if you don't click on the body element in 5 seconds the background color will be black.
Reference:
https://developer.mozilla.org/en/DOM/window.clearTimeout
https://developer.mozilla.org/En/Window.setTimeout
Note: setTimeout and clearTimeout are not ECMAScript native methods, but Javascript methods of the global window namespace.
You will have to remember the timeout "Timer", cancel it, then restart it:
g_timer = null;
$(document).ready(function() {
startTimer();
});
function startTimer() {
g_timer = window.setTimeout(function() {
window.location.href = 'file.php';
}, 115000);
}
function onClick() {
clearTimeout(g_timer);
startTimer();
}
var myTimer = setTimeout(..., 115000);
something.click(function () {
clearTimeout(myTimer);
myTimer = setTimeout(..., 115000);
});
Something along those lines!
For NodeJS it's super simple:
const timeout = setTimeout(...);
timeout.refresh();
From the docs:
timeout.refresh()
Sets the timer's start time to the current time, and reschedules the timer to call its callback at the previously specified duration adjusted to the current time. This is useful for refreshing a timer without allocating a new JavaScript object.
But it won't work in JavaScript because in browser setTimeout() returns a number, not an object.
This timer will fire a "Hello" alertbox after 30 seconds. However, everytime you click the reset timer button it clears the timerHandle then re-sets it again. Once it's fired, the game ends.
<script type="text/javascript">
var timerHandle = setTimeout("alert('Hello')",3000);
function resetTimer() {
window.clearTimeout(timerHandle);
timerHandle = setTimeout("alert('Hello')",3000);
}
</script>
<body>
<button onclick="resetTimer()">Reset Timer</button>
</body>
var redirectionDelay;
function startRedirectionDelay(){
redirectionDelay = setTimeout(redirect, 115000);
}
function resetRedirectionDelay(){
clearTimeout(redirectionDelay);
}
function redirect(){
location.href = 'file.php';
}
// in your click >> fire those
resetRedirectionDelay();
startRedirectionDelay();
here is an elaborated example for what's really going on http://jsfiddle.net/ppjrnd2L/
i know this is an old thread but i came up with this today
var timer = []; //creates a empty array called timer to store timer instances
var afterTimer = function(timerName, interval, callback){
window.clearTimeout(timer[timerName]); //clear the named timer if exists
timer[timerName] = window.setTimeout(function(){ //creates a new named timer
callback(); //executes your callback code after timer finished
},interval); //sets the timer timer
}
and you invoke using
afterTimer('<timername>string', <interval in milliseconds>int, function(){
your code here
});
$(function() {
(function(){
var pthis = this;
this.mseg = 115000;
this.href = 'file.php'
this.setTimer = function() {
return (window.setTimeout( function() {window.location.href = this.href;}, this.mseg));
};
this.timer = pthis.setTimer();
this.clear = function(ref) { clearTimeout(ref.timer); ref.setTimer(); };
$(window.document).click( function(){pthis.clear.apply(pthis, [pthis])} );
})();
});
To reset the timer, you would need to set and clear out the timer variable
$time_out_handle = 0;
window.clearTimeout($time_out_handle);
$time_out_handle = window.setTimeout( function(){---}, 60000 );

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