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Disable the click and reset it (Javascript Vanilla)

I have a problem. I created the following code! when you click on a button, a timer that lasts 3 seconds starts, the problem is that if I double click the button, the seconds go crazy, I would like to make sure that the click is reset as soon as the timer reaches 0! so that clicking again the timer always starts from 3 seconds!
document.getElementById("titolo").style.display="block"
count = 3 ;
setInterval(function(){
count--;
if(count>=0){
id = document.getElementById("titolo");
id.innerHTML = count;
}
if(count === 0){
document.getElementById("titolo").style.display="none" ;
}
},1000);

setInterval returns an ID that you can pass to clearInterval to cancel it. When the user clicks, cancel the existing ID and call setInterval again to reset it.

Capture the return value of setInterval so that later you can use it to call clearInterval.
You should disable (or hide) the button (or other element) that the user can click to start the count down.
Make sure to always declare your variables with var, let or const.
Don't use innerHTML when you only want to assign text (not HTML entities). For text (like the string representation of a counter) use textContent.
Here is how it could work:
let start = document.getElementById("start");
let id = document.getElementById("titolo");
start.addEventListener("click", function () {
start.disabled = true;
id.style.display = "block";
id.textContent = "3";
let count = 3;
let timer = setInterval(function(){
count--;
id.textContent = count;
if (count === 0) {
id.style.display = "none" ;
clearInterval(timer);
start.disabled = false;
}
}, 1000);
});
<button id="start">Start</button>
<div id="titolo"></div>

The function setInterval returns the unique id representing the interval. You can call the function clearInterval to delete that interval.
Example:
var intervalID = setInterval(function () { }, 0);
clearInterval(intervalID);
Example combined with your code:
var intervalID, count, dom = document.querySelector("#titolo");
document.querySelector("#button").addEventListener("click", onClick);
function onClick() {
clearInterval(intervalID);
dom.style.display = "block";
dom.textContent = 3;
count = 3;
intervalID = setInterval(function() {
count -= 1;
if (count >= 0) dom.textContent = count;
else {
dom.style.display = "none";
clearInterval(intervalID);
}
}, 1000);
}
<div id="titolo"></div>
<button id="button">Button</button>

Starting timer when clicking first card of memory game

Ok I am trying to wrap up a project and the only thing holding me back is it that they call for the timer to start on clicking a match game. The timer starts when the HTML file loads which is not what the project wants and I have tried some methods but ends up freezing the game. I want the timer to be able to start when clicking a card.
var open = [];
var matched = 0;
var moveCounter = 0;
var numStars = 3;
var timer = {
seconds: 0,
minutes: 0,
clearTime: -1
};
//Start timer
var startTimer = function () {
if (timer.seconds === 59) {
timer.minutes++;
timer.seconds = 0;
} else {
timer.seconds++;
};
// Ensure that single digit seconds are preceded with a 0
var formattedSec = "0";
if (timer.seconds < 10) {
formattedSec += timer.seconds
} else {
formattedSec = String(timer.seconds);
}
var time = String(timer.minutes) + ":" + formattedSec;
$(".timer").text(time);
};
This is the code for clicking on a card. I have tried to include a startTimer code into this but doesn't work.
var onClick = function() {
if (isValid( $(this) )) {
if (open.length === 0) {
openCard( $(this) );
} else if (open.length === 1) {
openCard( $(this) );
moveCounter++;
updateMoveCounter();
if (checkMatch()) {
setTimeout(setMatch, 300);
} else {
setTimeout(resetOpen, 700);
}
}
}
};
And this class code I use for my HTML file
<span class="timer">0:00</span>

Try this: https://codepen.io/anon/pen/boWQbe
All you needed to do was remove resetTimer() call from the function that happens on page load and then just do a check in the onClick (of card) to see if the timer has started yet. timer.seconds == 0 && timer.minutes == 0.

Javascript vanilla (jquery not preferred)

I'd like to know how to take this code I found here
http://jsfiddle.net/T42jj/
var imageGallery = [
"http://placehold.it/350x150",
"http://placehold.it/350x250",
"http://placehold.it/350x350",
"http://placehold.it/350x450"
];
var imgCount = 0; var totalImgs = imageGallery.length - 1; var timer;
function next() {
timer = setInterval(function fn() {
imgCount++;
if (imgCount > totalImgs) imgCount = 0
document.getElementById("gallery").src = imageGallery[imgCount];
return fn;
}(), 500)
}
function previous() {
timer = setInterval(function fn() {
console.log('prev')
imgCount--;
if (imgCount < 0) imgCount = totalImgs;
document.getElementById("gallery").src = imageGallery[imgCount];
return fn;
}(), 100)
}
function stopInterval() {
clearInterval(timer)
}
window.onmouseup = stopInterval;
and changing the "onMousedown" to onmouseOver so it continuously loops as you mouse over, which I've managed to do.
Then adding a stop function button that works
onmouseClick
Back
Stop
with a Stop function breaking the loop. e.g break;
sorry i cant figure out how to format any of this. this is the worst system ever.
does this [code] work? [/code]
or something like it?
basically look at the jsfiddle code and help me if you could make a function that stops the loop from infinitely repeating images when a mouse click event occurs.

How to change the speed of setInterval in real time

I would like to know how to change the speed of setInterval in real time e.g:
if (score < 10)
repeater = setInterval(function() {
spawnEnemy();
}, 1000);
if (score => 10)
repeater = setInterval(function() {
spawnEnemy();
}, 500);
I know this method doesn't work, but is there a way that I can achieve this some other way?

jsFiddle Demo
There is no way to change the interval speed itself once running. The only way to do it is to have a variable for the speed, and then clear the interval and start a new one with the new speed.
var speed = 500;
var changeSpeed = speed;
repeater = setInterval(repeaterFn, speed);
function repeaterFn(){
spawnEnemy();
if( changeSpeed != speed ){
clearInterval(repeater);
speed = changeSpeed;
repeater = setInterval(repeaterFn, speed);
}
}
function changeRepeater(){
changeSpeed = 700;
}

Another way would be to just use setTimeout rather than setInterval. Do the check every time so you can keep your speed logic in a seperate function.
var game_over = false;
var score = 0;
function getSpeedFromScore(score)
{
if (score > 20) {
game_over = true;
}
if (score < 10) {
return 1000;
} else {
return 500;
}
}
function spawnEnemyThenWait() {
if (!game_over) {
spawnEnemy();
var speed = getSpeedFromScore(score);
setTimeout(spawnEnemyThenWait, speed);
}
}
JS Fiddle http://jsfiddle.net/bq926xz6/

You can use clearInterval:
if (score < 10) {
clearInterval(repeater);
repeater = setInterval(spawnEnemy, 1000);
}
if (score => 10) {
clearInterval(repeater);
repeater = setInterval(spawnEnemy, 500);
}
But it depends on the context. If this snippet is executed more often, than it has to be, you will need some kind of mechanism to prevent it from resetting your interval all the time.
But there is (as I wrote in the comment to the question) no way to use clearInterval and change the interval itself. At least not without replacing it by a new interval as shown above.

You can use a game loop and track the spawn state in an enemy class:
// press f12 so see console
function Enemy() {
this.spawned = false;
this.spawnOn = 20;
this.tick = function () {
this.spawnOn = this.spawnOn - 1;
if (this.spawnOn == 0) {
this.spawned = true;
}
}
this.goBackToYourCage = function () {
this.spawnOn = Math.floor(Math.random() * 50) + 1;
this.spawned = false;
}
}
var enemy = new Enemy();
window.setInterval(function () {
enemy.tick();
if (enemy.spawned) {
console.log('spawned');
enemy.goBackToYourCage();
console.log('Next spawin in :' + enemy.spawnOn);
}
}, 100);
http://jsfiddle.net/martijn/qxt2fe8y/2/

Casino Roulette Game not working

http://csdev.cegep-heritage.qc.ca/students/cguigue/primordialCasino/game.html
supposed to click on the spin button and it should start the wheel spinning as well as changed the text on the screen in my displayArea, though when i click spin nothing happens,
getting undefined type error on the following code and not sure as to why
$('#wheel').rotate({
angle: 0,
animateTo: 2520,
duration: 4000
});
it says it isn't a function... :S
also...
if(currentGame.place == 0 && cellText == 0)
{
currentGame.setBet(betAmount * 40);
}
function rouletteGame(num, even, col)
{
this.place = num;
this.isEven = even;
this.colour = col;
this.win = 0;
this.hasBet = false;
this.setBet = function(bet)
{
this.win += bet;
this.hasBet = true;
}
says currentGame.place is undefined
but im initializing it in a for loop and its calling my above function...
for (var i = 1; i < rouletteWheel.length; ++i)
{
place = i;
if(i % 2 == 1)
{
isEven = false;
}
else
{
isEven = true;
}
if( i = red[count])
{
colour = "red";
++count;
}
else
{
colour = "black";
}
rouletteWheel[i] = new rouletteGame(place, isEven, colour);
}// for ()

.rotate() is not a built-in JQuery plugin. You will need to download or link the plugin in order for it to work. Add the following in your element of the HTML:
<script type="text/javascript" src="http://jqueryrotate.googlecode.com/svn/trunk/jQueryRotate.js"></script>
and see if that helps. with the first part of your problem.
As for the second part, I'm not sure if Javascript works this way too (I think it does), but you should create the new roulette game outside of the loop, and only change the values inside. Otherwise you are only creating a new roulette game for use within the scope of the for loop, not outside.
May want to check the documentation for this, as I'm not 100% positive about it. I just know it's how most other languages work.