var checkduplicates = new Array();
drawOne(i);
//console.log(checkduplicates)
function drawOne(i)
{
//randomly select one photo
var picinfo = photos[Math.floor(Math.random()*photos.length)];
//check duplicates pic, if duplicates exist, get another one
while(checkduplicates.indexOf(picinfo)!=-1||picinfo.title.length>10)
{
picinfo = photos[Math.floor(Math.random()*photos.length)];
}
checkduplicates.push(picinfo);
var ctx = document.getElementsByClassName("canvas")[i].getContext('2d');
var img = new Image();
//get the pic URL
img.src = "http://farm" + picinfo.farm + ".static.flickr.com/"
+ picinfo.server + "/" + picinfo.id + "_" + picinfo.secret + "_m.jpg";
img.onload = function()
{
// Draw pieces
ctx.drawImage(img,0,0,132,150);
ctx.drawImage(frame,0,0,133,152);
if(picinfo.title=="")
$("#"+i).append("Untitled");
else
$("#"+i).append(picinfo.title);
i++;
if (i != canvaslength)
{
drawOne(i);
}
}
What I am doing here is that I am dynamically generate pictures to fill out 16 canvas and some people said that I am using asynchronous recursion which I dont even notice. I have tried to use loop instead of recursion but somehow ended it up getting exception that i dont know how to fix. So I stick to recursion. However, my problem is that how I can detect the end of the recursion like the commented line shows there is only one item in the array.
//console.log(checkduplicates)
and the explanation I got is that as I understand, the commented console.log is executed before a bunch of recursion of drawOne function finished But what I wanted was that I wanted the full 16 images to be fully loaded and then select them so that I can do something with them. Therefore, the question is how I can detect the end of the recursion. Thank you. You are welcomed to ignore most of my codes and just look at the recursion part.
This is not 'asynchronous recursion'. That would imply that at least two of these loops are running at the same time, and they return asynchronously. Which is simply not the case.
Basically the only time you STOP recursion is when i == canvaslength.
So, just take that if statement.
if (i != canvaslength)
{
drawOne(i);
}else{
console.log('recursion is done') // do what you want here.
}
Related
With the below code:
$('#button').on('click', function () {
var longArray = searchArray; // assume this has 100 or more postalcodes init
var shortArrays = [], i, len;
for (i = 0, len = longArray.length; i < len; i += 100) {
shortArrays.push(longArray.slice(i, i + 100));
}
// Now we iterate over shortArrays which is an array of arrays where each array has 100 or fewer
// of the original postalcodes in it
for (i = 0, len = shortArrays.length; i < len; i++) {
// shortArrays[i] is an array of postalcodes of 100 or less
$.each(shortArrays[i], function(index, value){
setTimeout( function() {
// Each parent gets its own searchToggle class
$('.postcodes input[data-postcode*="' + value + '"]').parent().parent().addClass('searchToggle');
// Each parent also gets a data filter attribute for ordering the results
$('.postcodes input[data-postcode*="' + value + '"]').parent().parent().attr('data-filter' , index);
// We display the items in the search array
$('.postcodes input[data-postcode*="' + value + '"]').parent().parent().css('display', 'flex');
$('.postcodes .searchToggle .postcode input[data-postcode*="' + value + '"]').parent().css('display', 'flex');
}, 0 );
})
} // /for
alert('Finished message');
});
I try to show an alert message(for debugging) once the $.each() is finished. Since this each goes through an array that could be 1000s of postal codes long I broke it up in chunks of 100. This to prevent the dreaded browser is unresponsive. This is all working fine but the alert fires immediately on click.
I have tried several things already:
I tried by using a count: ABOVE THE EACH var count = 0; INSIDE THE EACH count++ if ( count == longArray.length ) { ALERT } But this also fired the alert immediately???
I tried it by using an interval but that became a mess almost instantly.
I tried a couple of other SO answers but all of them resulted in the alert to fire immediately.
When looking through the jQuery docs and previous codes that I have written it should just run the code after the each is finished but in this case it does not.
Any idea on why this is and how I can fix it.
PS: This alert could be other codes! Like sorting the results or something else.
PS2: I can change all the js/jQuery you see but I cannot change any of the HTML selectors.
PS3: Thank you for thinking about this issue and especially for commenting/answering!
I have solved it by adding another setTimeout.
So I replaced the alert (see Question) from
alert(Finished message);
To
setTimeout( function() {
// As an example I used alert in my question and here in this answer.
// This can be offcourse anything else. I use it for instance to sort the results.
alert(Finished message);
}, 0 );
This works for me, but it might not be the best way to deal with it. So I am still looking forward to what more experienced people think about the question or the answer.
This question already has answers here:
Best way to iterate over an array without blocking the UI
(4 answers)
Closed 6 years ago.
In my application I have a very big array (arround 60k records). Using a for loop I am doing some operations on it as shown below.
var allPoints = [];
for (var i = 0, cLength = this._clusterData.length; i < cLength; i+=1) {
if (allPoints.indexOf(this._clusterData[i].attributes.PropertyAddress) == -1) {
allPoints.push(this._clusterData[i].attributes.PropertyAddress);
this._DistClusterData.push(this._clusterData[i])
}
}
When I run this loop the browser hangs as it is very big & in Firefox is shows popup saying "A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete". What can I do so that browser do not hang?
You need to return control back to the browser in order to keep it responsive. That means you need to use setTimeout to end your current processing and schedule it for resumption sometime later. E.g.:
function processData(i) {
var data = clusterData[i];
...
if (i < clusterData.length) {
setTimeout(processData, 0, i + 1);
}
}
processData(0);
This would be the simplest thing to do from where you currently are.
Alternatively, if it fits what you want to do, Web Workers would be a great solution, since they actually shunt the work into a separate thread.
Having said this, what you're currently doing is extremely inefficient. You push values into an array, and consequently keep checking the ever longer array over and over for the values it contains. You should be using object keys for the purpose of de-duplication instead:
var allPoints = {};
// for (...) ...
if (!allPoints[address]) { // you can even omit this entirely
allPoints[address] = true;
}
// later:
allPoints = allPoints.keys();
First of all, avoid the multiple this._clusterData[i] calls. Extract it to a variable like so:
var allPoints = [];
var current;
for (var i = 0, cLength = this._clusterData.length; i < cLength; i+=1) {
current = this._clusterData[i];
if (allPoints.indexOf(current.attributes.PropertyAddress) == -1) {
allPoints.push(current.attributes.PropertyAddress);
this._DistClusterData.push(current)
}
}
This should boost your performance quite a bit :-)
As others already pointed out, you can do this asynchronously, so the browser remains responsive.
It should be noted however that the indexOf operation you do can become very costly. It would be better if you would create a Map keyed by the PropertyAddress value. That will take care of the duplicates.
(function (clusterData, batchSize, done) {
var myMap = new Map();
var i = 0;
(function nextBatch() {
for (data of clusterData.slice(i, i+batchSize)) {
myMap.set(data.attributes.PropertyAddress, data);
}
i += batchSize;
if (i < clusterData.length) {
setTimeout(nextBatch, 0);
} else {
done(myMap);
}
})();
})(this._clusterData, 1000, function (result) {
// All done
this._DistClusterData = result;
// continue here with other stuff you want to do with it.
}.bind(this));
Try considering adding to the array asynchronously with a list, for a set of 1000 records at a time, or for what provides the best performance. This should free up your application while a set of items is added to a list.
Here is some additional information: async and await while adding elements to List<T>
I'm trying (without much success) to create an array which contains slides being loaded into an iframe. One of these frames (/Events.php) uses PHP to query a WordPress database and show 1 post chosen at random. This slide needs to show a different random post every time the array loops through.
My code at them moment is...
<script type="text/javascript">
var frames = Array(
'http://www.example.com/Slide01.php', 5,
'http://www.example.com/Slide02.php', 5,
getRandomUrl(), 5,
'http://www.example.com/Slide04.php', 5
);
var i = 0, len = frames.length;
function getRandomUrl()
{
return "http://www.example.com/Events.php?=" + (new Date().getTime());
}
function ChangeSrc()
{
if (i >= len) { i = 0; } // start over
document.getElementById('myiframe').src = frames[i++];
setTimeout('ChangeSrc()', (frames[i++]*1000));
}
window.onload = ChangeSrc;
</script>
The only trouble is everytime /Events.php is shown it has the same number appended to it so therefore shows the same post in each loop.
I need to append a different number to the /Events.php slide on each loop so it generates different content each time.
I'm starting to think I'm approaching this in totally the wrong way so any help or pointers in the right direction would be appreciated!
Cheers,
Mark.
The issue is you are only calling getRandomUrl() once which is when you defined your array, this means the value will always be the same as its only returned once.
One solution would be to store the function itself in your array like so:
var frames = Array(
'http://www.example.com/Slide01.php', 5,
'http://www.example.com/Slide02.php', 5,
getRandomUrl, 5,
'http://www.example.com/Slide04.php', 5
);
And then call it in ChangeSrc() if its a function
function ChangeSrc()
{
if (i >= len) { i = 0; } // start over
var frame = frames[i++],
isFnc = typeof(frame) == "function";
if(isFnc){
frame = frame();
}
document.getElementById('myiframe').src = frame;
setTimeout(function(){
ChangeSrc()
}, frames[i++]*1000);
}
http://jsfiddle.net/redgg6pq/
A tip would be that you are only calling 'getRandomUrl' once, hence why it's always the same image. You want to call it each time you are in the loop.
I would suggest removing it from the static array, and calling it in the loop - does that make sense? :)
HTH
Okay, I hope you don't all facepalm when you see this - I'm still finding my way around javascript.
I am putting together an RSVP form for a wedding website.
I want the guests to be able to add their names to the RSVP form, but only have as many fields showing as required. To this end, after each name field, there is a link to click, which will, when clicked, show a name field for the next guest.
The code below works... but I am sure it can be tidier.
I have tried to insert a for() loop into the code in several different ways, I can see that the for() loop increments correctly to the last value - but when it does so, it leaves only the last addEventListener in place. I can only assume, that I should be using a different kind of loop - or a different approach entirely.
How should I tidy up the following?
<script>
function showNextGuest(i) {
document.getElementsByTagName(\'fieldset\')[i].style.display = \'block\';
}
function initiateShowNextGuest() {
document.getElementsByTagName('fieldset')[0].getElementsByTagName('a')[0].addEventListener('click',function(){showNextGuest(1);},false);
document.getElementsByTagName('fieldset')[1].getElementsByTagName('a')[0].addEventListener('click',function(){showNextGuest(2);},false);
document.getElementsByTagName('fieldset')[2].getElementsByTagName('a')[0].addEventListener('click',function(){showNextGuest(3);},false);
document.getElementsByTagName('fieldset')[3].getElementsByTagName('a')[0].addEventListener('click',function(){showNextGuest(4);},false);
document.getElementsByTagName('fieldset')[4].getElementsByTagName('a')[0].addEventListener('click',function(){showNextGuest(5);},false);
}
window.onload = initiateShowNextGuest();
</script>
Your intuition is right - a for loop could indeed simplify it and so could a query selector:
var fieldsSet = document.querySelectorAll("fieldset"); // get all the field sets
var fieldss = [].slice.call(asSet); // convert the html selection to a JS array.
fields.map(function(field){
return field.querySelector("a"); // get the first link for the field
}).forEach(function(link, i){
// bind the event with the right index.
link.addEventListener("click", showNextGuest.bind(null, i+1), false);
});
This can be shortened to:
var links = document.querySelectorAll("fieldset a:first-of-type");
[].forEach.call(links, function(link, i){
link.addEventListener("click", showNextGuest.bind(null, i+1), false);
});
function nextGuest () {
for(var i = 0; i < 5; i++){
document.getElementsByTagName('fieldset')[i]
.getElementsByTagName('a')[0]
.addEventListener('click',function(){
showNextGuest(parseInt(i + 1));
}, false);
}
}
Benjamin's answer above is the best given, so I have accepted it.
Nevertheless, for the sake of completeness, I wanted to show the (simpler, if less elegant) solution I used in the end, so that future readers can compare and contrast between the code in the question and the code below:
<script>
var initiateShowNextGuest = [];
function showNextGuest(j) {
document.getElementsByTagName('fieldset')[j].style.display = 'block';
}
function initiateShowNextGuestFunction(i) {
return function() {
var j = i + 1;
document.getElementsByTagName('fieldset')[i].getElementsByTagName('a')[0].addEventListener('click',function(){showNextGuest(j);},false);
};
}
function initiateShowNextGuests() {
for (var i = 0; i < 5; i++) {
initiateShowNextGuest[i] = initiateShowNextGuestFunction(i);
initiateShowNextGuest[i]();
}
}
window.onload = initiateShowNextGuests();
</script>
In summary, the function initiateShowNextGuests() loops through (and then executes) initiateShowNextGuestFunction(i) 5 times, setting up the 5 anonymous functions which are manually written out in the code in the original question, while avoiding the closure-loop problem.
I am having a strange issue, but it is not surprising as I am a bit of a JavaScript newbie. Basically I am creating a simple high-low card game. (Draw two cards, highest card wins). Anyways, the code is below.
The basic flow of the program is pretty simple. I choose 2 random numbers (1-52). These numbers are mapped to a corresponding card. (i.e. number 1 is the ace of spades, number 37 is the jack of clubs, etc.). Anyways, after drawing the cards, the program is to display the corresponding card and determine the winner. At the end of all of this, i have an alert that comes up and and tells the winner of the draw and asks if the user wants to play again.
The problem I am having is this: Even though the program should have already displayed the image of the card and output the results to a text area, the alert box shows up before any of that actually occurs and never displays the cards or the results. Any ideas? I am posting all of the code so far and any help would be appreciated. Thanks in advance.
function drawCards() {
var oppCard = randNumber();
var customerCard = randNumber();
while (oppCard == customerCard) {
customerCard = randNumber();
}
var oppCardName = displayCard(oppCard, "oppImage");
var customerCardName = displayCard(customerCard, "custImage");
var result2 = "Your card was: " + customerCardName;
var result1 = "The opponent's card was: " + oppCardName;
var result3 = determineWinner(oppCard, customerCard);
var result4 = result3 + '\n' + result1 + '\n' + result2;
$("#textareaRes").text(result4);
playAgain(result3);
}
function determineWinner(oppsCard, customersCard) {
var oppValue = oppsCard % 13;
var customerValue = oppsCard % 13;
var winnerString = "";
if (oppValue == 0) {
oppValue = 13;
}
if (customerValue == 0) {
customerValue = 13;
}
if (oppValue == customerValue) {
winnerString = "You Tied.";
}
else if (oppValue > customerValue) {
winnerString = "You Lose.";
}
else if (oppValue < customerValue) {
winnerString = "You Win!!";
}
return winnerString;
}
function randNumber() {
var min = 1;
var max = 52;
var random = Math.floor(Math.random() * (max - min + 1)) + min;
return random;
}
function playAgain(resultString) {
if (resultString == "You Lose." || resultString == "You Win!!") {
alert(resultString);
var conf = confirm("Play Again?");
if (conf == true) {
$("#textareaRes").text("");
document.getElementById("custImage").src="./cardImages/default.png";
document.getElementById("oppImage").src="./cardImages/default.png";
}
else {
window.location = "#mainMenuPage";
}
}
else {
alert(resultString);
alert("Try Again.");
$("#textareaRes").text("");
document.getElementById("custImage").src="./cardImages/default.png";
document.getElementById("oppImage").src="./cardImages/default.png";
}
}
So I did not place the code in here for the display card function, just because for testing it is exceptionally long. It is just a giant switch case for all 52 random numbers. The finished product will actually be pulling from an XML file, but I used this just for testing purposes. (If, for some reason, you need to see the display cards function, let me know and I can post it.) Anyway, to recap, the last call made in the drawCards() function is the playAgain function. Upon running this code the results nor the card images are displayed. It just jumps straight to the alert that is called for by the playAgain function. This is probably a pretty noobish question, but I am a little perplexed by it. So any help you guys can offer would be GREATLY appreciated. Thanks.
EDIT: It actually performs correctly in a computer's browser. However, the problem happens on a mobile device like a phone or tablet. So this is probably something that I am doing incorrectly here. Any help is greatly appreciated.
Changes in the browser doesn't show up as long as your Javascript code is running.
The browser is event driven, so changing an element in the DOM doesn't show the change immediately, instead an event is triggered to redraw the element. When your function has finished running, the browser will handle any pending events and show the changes.
So, when building an application, you have to use the same approach so that the browser has a chance to show the changes.
For anyone who finds this looking for the solution to the problem, the solution can be found in this answer: https://stackoverflow.com/a/13338585/870729
Here is a working fiddle of a simple example:
jQuery(function($) {
$.when($('#empty-me').html('')).done(function() {
alert('I did it!');
});
});
"./cardImages/default.png"
im not sure ... but try "../cardImages/default.png" ... i always use 2 dots for come to a higher level