Pure Javascript Fading in and fading out not working - javascript

I'm trying to create fade in and fade out function with JavaScript, but it's not working. Please tell me what I'm doing wrong.I'm not getting transitioning effect.
var fade_in_btn = document.getElementById('fade-in'),
fade_out_btn = document.getElementById('fade-out'),
fading_div = document.getElementById('fading-div');
function sleep(milliseconds) {
var start = new Date().getTime();
for (var i = 0; i < 1e7; i++) {
if ((new Date().getTime() - start) > milliseconds){
break;
}
}
}
fade_out_btn.onclick = function(){
for (var i=100; i >= 0; i--) {
sleep(0010);
opacity_function(i);
}
}
fade_in_btn.onclick = function(){
for (var i=1; i <= 100; i++) {
sleep(0010);
opacity_function(i);
}
}
function opacity_function(opacity_value){
fading_div.style.opacity = opacity_value / 100;
fading_div.style.filter = 'alpha(opacity=' + opacity_value + ')';
console.log(fading_div.style.opacity);
}
Fiddle with HTML.
All code Working Fine. But from my point of view problem is the for...loop is not updating the value of opacity after each iteration; it's only updating the final value.
Please Help me to resolve this problem.

this is a pure JS answer that doesn't use requestAnimationFrame but i have chosen to discard your sleep function since it is an odd choice and bad practice (and yours doesn't work. also note that there can be no true sleep in JS.)
this works:
fade_out_btn.onclick = function(){
var i = 100;
var myint = setInterval(function(){
opacity_function(i);
i--;
if (i<0) clearInterval(myint);
console.log(i);
},10); //this is the number of ms between iterations of the codeblock in my setInterval function
}
[EDIT: some people were recommending setTimeout. I see no need for that, but in case you really want to use setTimeout, this is how I would do it:
var i = 100;
function fadeout(){
var myint = setTimeout(function(){
opacity_function(i);
i--;
if (i>0) fadeout();
},10);
}
fade_out_btn.onclick = fadeout;
notice two things:
1 - I pulled the definition of i outside of the function. you would have to be grabbing that value that you want to decrement from outside the function anyways, because your starting value for a fadeout would presumably not always be 100 but would be set to the current value of the opacity, i.e. the value of fading_div.style.opacity * 100.
2 - i bound a callback to the onclick.
regarding choosing between setInterval and setTimeout:
setInterval and setTimeout both simply schedule the execution of code. setInterval schedules events every x ms from when it is executed whereas a series of chained setTimeouts schedules an event in x ms, then executes again, then schedules another event in x ms. so there is a little bit of time overhead for setTimeout because the real time interval is x + (the time is takes to execute the codeblock once). it is possible have issues with using setInterval if the time it takes to execute once is larger than the specified interval but that would not affect such a simple program as yours. see here]

Related

Problem with SetTimeout function - no gap [duplicate]

This question already has answers here:
JavaScript closure inside loops – simple practical example
(44 answers)
Closed 7 years ago.
I have this script:
for (var i = 1; i <= 2; i++) {
setTimeout(function() { alert(i) }, 100);
}
But 3 is alerted both times, instead of 1 then 2.
Is there a way to pass i, without writing the function as a string?
You have to arrange for a distinct copy of "i" to be present for each of the timeout functions.
function doSetTimeout(i) {
setTimeout(function() {
alert(i);
}, 100);
}
for (var i = 1; i <= 2; ++i)
doSetTimeout(i);
If you don't do something like this (and there are other variations on this same idea), then each of the timer handler functions will share the same variable "i". When the loop is finished, what's the value of "i"? It's 3! By using an intermediating function, a copy of the value of the variable is made. Since the timeout handler is created in the context of that copy, it has its own private "i" to use.
Edit:
There have been a couple of comments over time in which some confusion was evident over the fact that setting up a few timeouts causes the handlers to all fire at the same time. It's important to understand that the process of setting up the timer — the calls to setTimeout() — take almost no time at all. That is, telling the system, "Please call this function after 1000 milliseconds" will return almost immediately, as the process of installing the timeout request in the timer queue is very fast.
Thus, if a succession of timeout requests is made, as is the case in the code in the OP and in my answer, and the time delay value is the same for each one, then once that amount of time has elapsed all the timer handlers will be called one after another in rapid succession.
If what you need is for the handlers to be called at intervals, you can either use setInterval(), which is called exactly like setTimeout() but which will fire more than once after repeated delays of the requested amount, or instead you can establish the timeouts and multiply the time value by your iteration counter. That is, to modify my example code:
function doScaledTimeout(i) {
setTimeout(function() {
alert(I);
}, i * 5000);
}
(With a 100 millisecond timeout, the effect won't be very obvious, so I bumped the number up to 5000.) The value of i is multiplied by the base delay value, so calling that 5 times in a loop will result in delays of 5 seconds, 10 seconds, 15 seconds, 20 seconds, and 25 seconds.
Update
Here in 2018, there is a simpler alternative. With the new ability to declare variables in scopes more narrow than functions, the original code would work if so modified:
for (let i = 1; i <= 2; i++) {
setTimeout(function() {
alert(i)
}, 100);
}
The let declaration, unlike var, will itself cause there to be a distinct i for each iteration of the loop.
You can use an immediately-invoked function expression (IIFE) to create a closure around setTimeout:
for (var i = 1; i <= 3; i++) {
(function(index) {
setTimeout(function() { alert(index); }, i * 1000);
})(i);
}
This's Because!
The timeout function
callbacks are all running well after the completion of the loop. In fact,
as timers go, even if it was setTimeout(.., 0) on each iteration, all
those function callbacks would still run strictly after the completion
of the loop, that's why 3 was reflected!
all two of those functions, though they are defined
separately in each loop iteration, are closed over the same shared global
scope, which has, in fact, only one i in it.
the Solution's declaring a single scope for each iteration by using a self-function executed(anonymous one or better IIFE) and having a copy of i in it, like this:
for (var i = 1; i <= 2; i++) {
(function(){
var j = i;
setTimeout(function() { console.log(j) }, 100);
})();
}
the cleaner one would be
for (var i = 1; i <= 2; i++) {
(function(i){
setTimeout(function() { console.log(i) }, 100);
})(i);
}
The use of an IIFE(self-executed function) inside each iteration created a new scope for each
iteration, which gave our timeout function callbacks the opportunity
to close over a new scope for each iteration, one which had a variable
with the right per-iteration value in it for us to access.
The function argument to setTimeout is closing over the loop variable. The loop finishes before the first timeout and displays the current value of i, which is 3.
Because JavaScript variables only have function scope, the solution is to pass the loop variable to a function that sets the timeout. You can declare and call such a function like this:
for (var i = 1; i <= 2; i++) {
(function (x) {
setTimeout(function () { alert(x); }, 100);
})(i);
}
You can use the extra arguments to setTimeout to pass parameters to the callback function.
for (var i = 1; i <= 2; i++) {
setTimeout(function(j) { alert(j) }, 100, i);
}
Note: This doesn't work on IE9 and below browsers.
ANSWER?
I'm using it for an animation for adding items to a cart - a cart icon floats to the cart area from the product "add" button, when clicked:
function addCartItem(opts) {
for (var i=0; i<opts.qty; i++) {
setTimeout(function() {
console.log('ADDED ONE!');
}, 1000*i);
}
};
NOTE the duration is in unit times n epocs.
So starting at the the click moment, the animations start epoc (of EACH animation) is the product of each one-second-unit multiplied by the number of items.
epoc: https://en.wikipedia.org/wiki/Epoch_(reference_date)
Hope this helps!
You could use bind method
for (var i = 1, j = 1; i <= 3; i++, j++) {
setTimeout(function() {
alert(this);
}.bind(i), j * 100);
}
Well, another working solution based on Cody's answer but a little more general can be something like this:
function timedAlert(msg, timing){
setTimeout(function(){
alert(msg);
}, timing);
}
function yourFunction(time, counter){
for (var i = 1; i <= counter; i++) {
var msg = i, timing = i * time * 1000; //this is in seconds
timedAlert (msg, timing);
};
}
yourFunction(timeInSeconds, counter); // well here are the values of your choice.
I had the same problem once this is how I solved it.
Suppose I want 12 delays with an interval of 2 secs
function animate(i){
myVar=setTimeout(function(){
alert(i);
if(i==12){
clearTimeout(myVar);
return;
}
animate(i+1)
},2000)
}
var i=1; //i is the start point 1 to 12 that is
animate(i); //1,2,3,4..12 will be alerted with 2 sec delay
the real solution is here, but you need to be familiar with PHP programing language.
you must mix PHP and JAVASCRIPT orders in order to reach to your purpose.
pay attention to this :
<?php
for($i=1;$i<=3;$i++){
echo "<script language='javascript' >
setTimeout(function(){alert('".$i."');},3000);
</script>";
}
?>
It exactly does what you want, but be careful about how to make ralation between
PHP variables and JAVASCRIPT ones.

Why var defined value at the end of for loop prints a number bigger than what it is supposed to [duplicate]

This question already has answers here:
JavaScript closure inside loops – simple practical example
(44 answers)
Closed 7 years ago.
I have this script:
for (var i = 1; i <= 2; i++) {
setTimeout(function() { alert(i) }, 100);
}
But 3 is alerted both times, instead of 1 then 2.
Is there a way to pass i, without writing the function as a string?
You have to arrange for a distinct copy of "i" to be present for each of the timeout functions.
function doSetTimeout(i) {
setTimeout(function() {
alert(i);
}, 100);
}
for (var i = 1; i <= 2; ++i)
doSetTimeout(i);
If you don't do something like this (and there are other variations on this same idea), then each of the timer handler functions will share the same variable "i". When the loop is finished, what's the value of "i"? It's 3! By using an intermediating function, a copy of the value of the variable is made. Since the timeout handler is created in the context of that copy, it has its own private "i" to use.
Edit:
There have been a couple of comments over time in which some confusion was evident over the fact that setting up a few timeouts causes the handlers to all fire at the same time. It's important to understand that the process of setting up the timer — the calls to setTimeout() — take almost no time at all. That is, telling the system, "Please call this function after 1000 milliseconds" will return almost immediately, as the process of installing the timeout request in the timer queue is very fast.
Thus, if a succession of timeout requests is made, as is the case in the code in the OP and in my answer, and the time delay value is the same for each one, then once that amount of time has elapsed all the timer handlers will be called one after another in rapid succession.
If what you need is for the handlers to be called at intervals, you can either use setInterval(), which is called exactly like setTimeout() but which will fire more than once after repeated delays of the requested amount, or instead you can establish the timeouts and multiply the time value by your iteration counter. That is, to modify my example code:
function doScaledTimeout(i) {
setTimeout(function() {
alert(I);
}, i * 5000);
}
(With a 100 millisecond timeout, the effect won't be very obvious, so I bumped the number up to 5000.) The value of i is multiplied by the base delay value, so calling that 5 times in a loop will result in delays of 5 seconds, 10 seconds, 15 seconds, 20 seconds, and 25 seconds.
Update
Here in 2018, there is a simpler alternative. With the new ability to declare variables in scopes more narrow than functions, the original code would work if so modified:
for (let i = 1; i <= 2; i++) {
setTimeout(function() {
alert(i)
}, 100);
}
The let declaration, unlike var, will itself cause there to be a distinct i for each iteration of the loop.
You can use an immediately-invoked function expression (IIFE) to create a closure around setTimeout:
for (var i = 1; i <= 3; i++) {
(function(index) {
setTimeout(function() { alert(index); }, i * 1000);
})(i);
}
This's Because!
The timeout function
callbacks are all running well after the completion of the loop. In fact,
as timers go, even if it was setTimeout(.., 0) on each iteration, all
those function callbacks would still run strictly after the completion
of the loop, that's why 3 was reflected!
all two of those functions, though they are defined
separately in each loop iteration, are closed over the same shared global
scope, which has, in fact, only one i in it.
the Solution's declaring a single scope for each iteration by using a self-function executed(anonymous one or better IIFE) and having a copy of i in it, like this:
for (var i = 1; i <= 2; i++) {
(function(){
var j = i;
setTimeout(function() { console.log(j) }, 100);
})();
}
the cleaner one would be
for (var i = 1; i <= 2; i++) {
(function(i){
setTimeout(function() { console.log(i) }, 100);
})(i);
}
The use of an IIFE(self-executed function) inside each iteration created a new scope for each
iteration, which gave our timeout function callbacks the opportunity
to close over a new scope for each iteration, one which had a variable
with the right per-iteration value in it for us to access.
The function argument to setTimeout is closing over the loop variable. The loop finishes before the first timeout and displays the current value of i, which is 3.
Because JavaScript variables only have function scope, the solution is to pass the loop variable to a function that sets the timeout. You can declare and call such a function like this:
for (var i = 1; i <= 2; i++) {
(function (x) {
setTimeout(function () { alert(x); }, 100);
})(i);
}
You can use the extra arguments to setTimeout to pass parameters to the callback function.
for (var i = 1; i <= 2; i++) {
setTimeout(function(j) { alert(j) }, 100, i);
}
Note: This doesn't work on IE9 and below browsers.
ANSWER?
I'm using it for an animation for adding items to a cart - a cart icon floats to the cart area from the product "add" button, when clicked:
function addCartItem(opts) {
for (var i=0; i<opts.qty; i++) {
setTimeout(function() {
console.log('ADDED ONE!');
}, 1000*i);
}
};
NOTE the duration is in unit times n epocs.
So starting at the the click moment, the animations start epoc (of EACH animation) is the product of each one-second-unit multiplied by the number of items.
epoc: https://en.wikipedia.org/wiki/Epoch_(reference_date)
Hope this helps!
You could use bind method
for (var i = 1, j = 1; i <= 3; i++, j++) {
setTimeout(function() {
alert(this);
}.bind(i), j * 100);
}
Well, another working solution based on Cody's answer but a little more general can be something like this:
function timedAlert(msg, timing){
setTimeout(function(){
alert(msg);
}, timing);
}
function yourFunction(time, counter){
for (var i = 1; i <= counter; i++) {
var msg = i, timing = i * time * 1000; //this is in seconds
timedAlert (msg, timing);
};
}
yourFunction(timeInSeconds, counter); // well here are the values of your choice.
I had the same problem once this is how I solved it.
Suppose I want 12 delays with an interval of 2 secs
function animate(i){
myVar=setTimeout(function(){
alert(i);
if(i==12){
clearTimeout(myVar);
return;
}
animate(i+1)
},2000)
}
var i=1; //i is the start point 1 to 12 that is
animate(i); //1,2,3,4..12 will be alerted with 2 sec delay
the real solution is here, but you need to be familiar with PHP programing language.
you must mix PHP and JAVASCRIPT orders in order to reach to your purpose.
pay attention to this :
<?php
for($i=1;$i<=3;$i++){
echo "<script language='javascript' >
setTimeout(function(){alert('".$i."');},3000);
</script>";
}
?>
It exactly does what you want, but be careful about how to make ralation between
PHP variables and JAVASCRIPT ones.

How to exec a function after previous ends?

guys. It's a timer. I wanna run the timer and when it's end do something else(like a warning),and then run again with other amount of minutes. But I can't cause always only the second call is executed:
$(document).ready(function() {
timer(5,timer(25));
// timer(5);
// timer(25); do not work... only exec de last one
});
function timer(countTo,callback){
var time = 10; /* how long the timer runs for */
var initialOffset = '440';
var i = 1
var interval = setInterval(function() {
$('.circle_animation').css('stroke-dashoffset', initialOffset-(i*(initialOffset/countTo)));
$('h2').text(i);
if (i == countTo) {
clearInterval(interval);
}
i++;
}, 1000);
callback();
}
Which is the best solution? There is something that I am not understanding... Thanks anyway!
Well, first off:
timer(5,timer(25));
If you think this line will execute timer(5), and then at the end of timer(5) it will execute timer(25), you are mistaken. This is actually going to evaluate timer(25) immediately, and pass its return value (undefined) as the second parameter to timer(5,undefined).
If you intended to pass that as a callback, you need to pass a function. So you could do:
timer(5,timer.bind(null,25));
But, for that matter, you don't even check if callback exists before attempting to invoke it, so you probably are getting a reference error anyway.
timer(5,timer(25));
starts two timers and passes the result of the second (undefined) to the first as callback. You want:
timer(5,timer.bind(window,25));
And the callback needs to be executed if i==countTo ...
Is this what you want?
timer(5,function(){timer(25)});
Your problem is here:
timer(5,timer(25));
You should type
timer(5, function(){
timer(25)
});
//or using ES6 syntax
timer(5, () => timer(25));
because timer(25) returns its value (this function doesn't return value so it tries to invoke undefined), not that function.
Also read about closures, it might be helpful.
Instead of runing a callback(), you need to run the function itself (timer()). You'll also need to run a for loop inside your function that checks how many times the function has already run. If it reaches your desired maximum, break out of that. This way it won't run indefinitely.
In the following example, the timer() function executes five times, which is what I'm assuming you want by calling timer(5).
$(document).ready(function() {
timer(5);
});
function timer(countTo) {
for (var iterations = 0; iterations < countTo; iterations++) {
var time = 10; /* how long the timer runs for */
var initialOffset = '440';
var i = 1
var interval = setInterval(function() {
$('.circle_animation').css('stroke-dashoffset', initialOffset - (i * (initialOffset / countTo)));
$('h2').text(i);
if (i == countTo) {
clearInterval(interval);
}
}, 1000);
timer();
console.log("Iteration:", iterations + 1);
}
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
To run the function 25 times after this, all you have to do is call timer(25) directly after timer(5):
$(document).ready(function() {
timer(5);
timer(25);
});
$(document).ready(function() {
timer(5);
timer(25);
});
function timer(countTo) {
for (var iterations = 0; iterations < countTo; iterations++) {
var time = 10; /* how long the timer runs for */
var initialOffset = '440';
var i = 1
var interval = setInterval(function() {
$('.circle_animation').css('stroke-dashoffset', initialOffset - (i * (initialOffset / countTo)));
$('h2').text(i);
if (i == countTo) {
clearInterval(interval);
}
}, 1000);
timer();
console.log("Iteration:", iterations + 1);
}
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
Hope this helps! :)

Combine for loop with timing events in javascript

I have this code:
for (i = 0; i < 3; i++) {
var interval = setInterval(function(){
alert(i);
}, 2000);
}
What I would like to achieve is to have an alert every 2 sec displaying first 0, then 1 and lastly 2.
Instead I have to wait for quite long before I have 3 alerts all displaying the number 3. Where is my code wrong?
Well, there is (yet again) more than one solution to this problem. But, lets first talk why your code doesn't work properly.
Your code:
for (i = 0; i < 3; i++) {
var interval = setInterval(function(){
alert(i);
}, 2000);
}
..basically means that it will assign three setInterval calls to be executed after 2 seconds as fast as the for loop is placing them to the queue. So basically, all your calls runs really fast after 2 seconds, only few milliseconds or less between them. Moreover, setInterval means that it will be called as long as clearInterval is called to the variable it is assigned with. In other words, your code never stops executing the alert, because you are never calling clearInterval. Finally, your alert(i) will always display value of 3, because it is the last value of i when execution moves away from the for loop.
To improve your code, you could remove the for loop entirely and just let setInterval run as long as the value of i is alerted three times; At that point, you just call clearInterval to the value which has handle to setInterval and the job is finished.
Working code:
// value to output
var i = 0,
// starting setInterval and assigning its handle to variable interval,
// it is used to clear the interval when execution should be finished
interval = setInterval(function () {
// alert value of i and increase it by 1
alert(i++);
// if i is equals to 3, no more calls
if(i === 3) {
// clear the interval so method won't be called in the future
clearInterval(interval);
}
}, 2000);
JS FIDDLE EXAMPLE
Cheers, hopefully you learnt something new today.
Without forloop:
var number = 0;
var interval = setInterval(function(){
alert(number);
number++;
if(number === 3) {
clearInterval(interval);
}
}, 2000);
JSFIDDLE
1.1 Without for loop + without initial delay (demo):
var i = 0;
var showAlert = function(){
alert(i);
i++;
if(i < 3){
setTimeout(function(){
showAlert();
}, 2000);
}
};
showAlert();
1.2 Without for loop + with initial delay (demo):
var i = 0;
var showAlert = function(){
if(i < 3){
setTimeout(function(){
alert(i);
i++;
showAlert();
}, 2000);
}
};
showAlert();
2.1 With for loop + without initial delay (demo):
function setAlert(k){
setTimeout(function(){
alert(k);
},k * 2000);
}
for(var i = 0; i < 3; i++) {
setAlert(i);
}
2.2 With for loop + with initial delay (demo):
function setAlert(k){
setTimeout(function(){
alert(k);
},(k + 1) * 2000);
}
for(var i = 0; i < 3; i++) {
setAlert(i);
}
First of all, I would go with setTimout, you know that you want 3 alerts.
Second problem is a bit stranger. You are calling async function, setTimeout/setInterval and referring to the original i of the for loop inside of the setTimeout callback. That will not work because at the time of the timeout invocation the for loop has already finished and i var will be 3. One solution is to wrapp the async function in a self invoking anonymous function with params that you need inside async function. In our case we call it with i.
Solution:
for (i = 0; i < 3; i++) {
(function(i) {
setTimeout(function(){
alert(i);
}, 2000 * i);
})(i);
}
JS fiddle

setTimeout Cascading Animations with JavaScript

I'd like to add a class to a series of spans using setTimeout() such that the class is added in cascading fashion, creating a visual progression rather than having them all set at once. I've tried so many different ways.
Here's a codepen...
http://codepen.io/geirman/pen/nDhpd
The codepen tries to mimic a working example I've found here...
https://developers.google.com/maps/documentation/javascript/examples/marker-animations-iteration
The problem is that I can't seem to delay the addClass successively, so it happens all at once. Here's the current code.
/* The Problem Code
********************/
var span$ = $("span");
var index = 0;
var factor = 500;
function colorSpans(){
for(var i = 0; i < span$.length; i++){
setTimeout(function(){
animate();
}, factor*index);
}
index = 0;
}
function animate(){
span$[index++].className = "lg";
}
colorSpans();
One more thing, I'd love to do this sans jQuery, but will accept a jQuery solution as well.
In your current code, it looks like the very first call to animate will execute immediately, after which index will be 1. But the loop is likely to finish executing before the second timeout-handler is called (i.e., the loop won't take 500ms to execute). So this means that the remaining spans will appear instantaneously since the value of index will not be updated.
Something like this should work:
function colorSpans() {
for(var i = 0; i < span$.length; i++) {
(function(i) {
setTimeout(function() {
animate(i);
}, factor * i);
})(i); //force a new scope so that the "i" passed to animate()
//is the value of "i" at that current iteration and not
//the value of "i" when the loop is done executing.
}
}
function animate(i) {
span$[i].className = "lg";
}
The above code is also preferable because you're not using a global variable to maintain state between colorSpans and animate (i.e., we're not using index).
But you can make additional improvements by using setInterval instead:
var i = 0;
var intervalId = setInterval(function() {
if(i < span$.length) {
animate(i);
i++;
} else {
clearInterval(intervalId);
}
}, 500)
I think this is cleaner than the setTimeout approach.
Check out the updated codepens:
setTimeout approach
setInterval approach

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