Develop Reference

mxgraph infinite loops on apply

I am extending mxgraph delete control example to add delete like controls to nodes which are generated dynamically in my graph. The source code for the example is available here
The problem is in this part of the code -
// Overridden to add an additional control to the state at creation time
mxCellRendererCreateControl = mxCellRenderer.prototype.createControl;
mxCellRenderer.prototype.createControl = function(state)
{
mxCellRendererCreateControl.apply(this, arguments);
var graph = state.view.graph;
if (graph.getModel().isVertex(state.cell))
{
if (state.deleteControl == null)
mxCellRendererCreateControl.apply inside the overridden call back of createControl seems to work as intended (calls the original function before creating additional controls) with the initial state of the graph on load. But, once I add nodes dynamically to the graph and the callback is invoked by mxgraph's validate/redraw, the control goes into an infinite loop, where 'apply' function basically keeps calling itself (i.e, the callback).
I am a bit clueless because when I debug, the context(this) looks fine, but I can't figure out why instead of invoking the prototype method, it just keeps invoking the overridden function in a loop. What am I doing wrong?

It looks like you are not cloning your original function the right way, please try the following :
Function.prototype.clone = function() {
var that = this;
return function theClone() {
return that.apply(this, arguments);
};
};
Add that new method somewhere in your main code so it will available in the whole application, now you can change your code to :
// Overridden to add an additional control to the state at creation time
let mxCellRendererCreateControl = mxCellRenderer.prototype.createControl.clone();
mxCellRenderer.prototype.createControl = function(state) {
mxCellRendererCreateControl(state);
var graph = state.view.graph;
if (graph.getModel().isVertex(state.cell)) {
if (state.deleteControl == null) {
// ...
}
}
// ...
};
This should work if I understood your problem correctly, if it does not, please change the old function call back to the apply. Otherwise let me know if something different happened after the Function prototype change.

It seems that your overriding code is being called multiple times (adding a simple console.log before your overriding code should be enough to test this)
Try to ensure that the code that overrides the function only gets called once, or validate whether the prototype function is the original or yours.
Here is an example of how you can check if the function is yours or not
if (!mxCellRenderer.prototype.createControl.isOverridenByMe) {
let mxCellRendererCreateControl = mxCellRenderer.prototype.createControl;
mxCellRenderer.prototype.createControl = function(state) { /* ... */ };
mxCellRenderer.prototype.createControl.isOverridenByMe = true;
}
There are other ways, like using a global variable to check if you have overriden the method or not.
If this doesn't fix your issue, please post more about the rest of your code (how is this code being loaded/called would help a lot)

Javascript: Can't handle events for multiple instances

I have put together a fun API for game creation. In the code I create a prototype for Mover and then extend it with several specific prototypes (Gold, Monster, and Hero). Each one is based on a img tag with a given ID. I use type-specific information in the constructor and a single template method for each type. Most of the functional code in Mover depends on those type-specific details. I have included one example for simplicity.
I use method calls in a separate script to create and destroy instances of the Mover child types. When I create and destroy one instance at a time everything works as intended. The image updates, the sound plays and it is removed after the correct delay. If I create two or more, however, only the last one works as expected. So if I make gold, moster, hero. Only the hero will remove correctly. The other two will play the audio, but don't appear to update.
I ran into the same problem when I tried to attach a function to the onclick event for more than one instance. Only the last one worked and the others did nothing. Obviously I'm missing something about the way java handles method assignments. Any explanation you can offer would help.
Thanks,
BSD
function Mover()
{
}
Mover.prototype.InitTag = function()
{
this.HTMLtag.src=this.imageURL;
this.HTMLtag.style.position="absolute";
this.HTMLtag.style.width=characterSize;
this.HTMLtag.style.height=characterSize;
this.Position(Math.floor(Math.random()*(MaxW-characterSize)+(characterSize/2)),Math.floor(Math.random()*(MaxH-characterSize)+(characterSize/2)));
}
Mover.prototype.Destroy = function()
{
var disp = this.HTMLtag.display;
this.HTMLtag.src=this.destroyURL
this.HTMLtag.display = disp;
this.destroyAudio.play();
this.RemoveTag();
}
function Monster(id)
{
this.MonsterID = id;
this.HTMLtag = document.getElementById("monster"+id);
this.imageURL = "monster1.jpg";
this.destroyURL = "monster2.jpg";
this.destroyAudio = monsterAudio;
}
Monster.prototype = new Mover();
Monster.prototype.RemoveTag = function()
{
var mID = this.MonsterID;
setTimeout(function() {field.DeleteMonster(mID)}, 1000);
}
function Hero()
{
this.HTMLtag = document.getElementById("hero");
this.imageURL = "hero1.jpg";
this.destroyURL = "hero2.jpg";
this.destroyAudio = heroAudio;
}
Hero.prototype = new Mover();
Hero.prototype.RemoveTag = function()
{
setTimeout(function() {field.DeleteHero()}, 5000);
}
function Gold(id)
{
this.GoldID = id;
this.HTMLtag = document.getElementById("gold"+id);
this.imageURL = "gold1.jpg";
this.destroyURL = "gold2.jpg";
this.destroyAudio = goldAudio;
}
Gold.prototype = new Mover();
Gold.prototype.RemoveTag = function()
{
var mID = this.GoldID;
setTimeout(function() {field.DeleteGold(mID)}, 1000);
}
---------UPDATE UPDATE UPDATE-----------
I have at least partially fixed the problem. I have gotten it to work, but I still don't know why it didn't function as intended. I noticed that while my browser's (Chrome) developer tools could visually identify the most-recently-added Mover when it was being destroyed, it could not do so with the any other movers.
Tag of most recently added Mover can be identified in Chrome developer tools.
This suggested that Mover.HTMLtag was not actually the same as document.getElementById('mover1'). I was able to confirm this by looking at the variables in the GoldField.DeleteMover. At the line indicated mover.src has not changed, but movers[id].HTMLtag.src has been correctly updated. In the most-recently-added case they were both the same.
GoldField.prototype.DeleteMover = function(id)
{
var isHero = false;
if(this.Hero!=null && id==this.Hero.myID)
{
this.Hero = null;
isHero = true;
}
else if(this.Tower!=null && id==this.Tower.myID)
{
this.Tower = null;
}
var mover = document.getElementById("mover"+id);
if(!isHero)
{
this.tag.removeChild(mover);//<<< HERE HERE HERE HERE
delete this.movers[id];
}
}
So, I changed one line in Mover.Destroy. By finding the tag by ID and setting the src. I was able to reliable behavior. It would appear that Mover.HTMLtag is not reliable the same after the second Mover is added. Any explanation?
Mover.prototype.Destroy = function()
{
document.getElementById(this.HTMLtag.id).src=this.destroyURL;
this.HTMLtag.src=this.destroyURL;//old method
this.destroyAudio.play();
this.RemoveTag();
}
On suspicion that this might extend to other updates to this.HTMLtag I set up some basic movement of the Hero. It works great, but if you add one additional Mover of any kind it no longer moves. That narrows down the question considerably. Why would constructing a second Mover cause the prototype members to change?

So I debug your code and I found the cause of your problem. The problem was when you create a new instance of monster you storing a reference to it on the monster var. And when you delete it you don't delete / update the reference to it. So your delete function myField.DeleteMover(id) try to delete a monster already deleted. How to solve this.
// create an array to keep ref to our instances
var monsters= [];
// var monster = null;
function addMonster()
{
// monster = goldField.AddMonster();⏎
// push every monster in array
monsters.push(goldField.AddMonster());
}
function killMonster()
{
// if array.length is true
if (monsters.length) {
// call the destroy function on the last ref
monsters[monsters.length - 1].Destroy();
// remove the last ref from array using pop
monsters.pop();
}
//monster.Destroy();
}
This is working however I think all of this should be done in the objects itself. And you should not care about it here.
Another advice try to use more array methods. Avoid using delete on array index because it mess with index and count instead use splice(index, 1) same for add item in array use push instead of arbitrary index.
Anyway funny game! Good luck to finish it.
Edit, after your answer I go back an test.
To make it work I do this.
// First go inGoldField.prototype.DeleteMover and replace the ugly delete index by
this.movers.splice(id, 1);
// Then in the Mover.prototype.Destroy
// This part is a a little blurred for me.
// the current HTMLtag looks good but when I console.log like this
console.log('before', this.HTMLtag);
this.HTMLtag = document.querySelector("#mover" + this.myID);
console.log('after', this.HTMLtag);
// They are not equal look like the first is outdated
You should convert all your delete and add to splice and push methods.
This is just a quick debug I don't know why the selector is outdated.

So I check the code again and I make it work without refreshing the selector. The problem is caused by the creation of dom element with innerHTML.
First reset
this.HTMLtag.src=this.destroyURL
Then instead of
//Mover.prototype.Destroy
this.tag.innerHTML+="<img id='mover"+this.moverCount+"'>";
I create a img dom el.
var img = document.createElement("img");
img.setAttribute('id', 'mover' + this.moverCount);
this.tag.appendChild(img);
All Monsters are now deleted with the image.
I don't check for the hero but first you should update your innerHTML and reply if there is still a problem. I don't think there is any problem with some prototype.

How do I set up sequences of functions that I want executed in JavaScript?

I'm working on a JavaScript driven site where I will have a lot of stuff that need's to be executed in a certain order. A lot of the stuff involves animations and AJAX-loading. Some pseudo code could look like this:
Load JSON formated data
Generate HTML-elements using the loaded JSON data and render them inside a div
Make the elements inside the div scrollable using a jQuery UI slider
Randomize a number between 1 and the total number of loaded elements
Make the jQuery UI slider scroll (animate) to the element that represents the randomized number for a duration of 500 milliseconds
Load more JSON formated data
Replace other elements on the page
And so on...
Each step in this is wrapped in a function - one function loads the JSON data, another generates the HTML-elements, a third initializes the jQuery UI slider and so on. Encapsulating the code in functions makes the code easier to read for me, but above all I want to be able to call the functions in different orders depending on what happens on the page and I want to be sure that one function has finished running before the next one is executed.
If there was just regular functions that didn't involve AJAX or jQuery animations I'd just execute the functions I want to execute, one after the other. The problem is that I need to wait for the animations and data retrieving functions to finish before moving on. To aid me both the animation and AJAX methods in jQuery allow me to send along a callback. But here's where I get lost.
What I want it to do is the following:
Load JSON data. If the loading is successful, go on and...
Generate HTML-elements
Make the elements scrollble
Randomize a number between 1 and the total number of loaded elements and pass it to...
A function that makes the jQuery slider slide (animated) to the element. When the animation is finished...
Load more JSON formated data. If the loading is successful, go on and...
Replace other elements on the page
The ideal thing would be if I could set up this sequence/chain of events in one single place, for example inside an event handler. If I want to call the functions in a different order or not call all of them I would just set up a different sequence/chain. An example could be:
Randomize a number between 1 and the total number of loaded elements and pass it to...
A function that makes the jQuery slider slide (animated) to the element. When the animation is finished...
This means that I'd have to be in control over the callbacks in each step.
I hope you understand what I'm looking for. I want to control the entire execution sequence from a single function. This function would be "the conductor of the orchestra" and all the other functions would be the different instrument sections of the orchestra. This conductor functions need's ears so it can hear when the violinist is finished with her solo and can tell the horns to start playing. Excuse me for the corny allegory, but I hopes it makes it easier to understand what I want to do.
Thanks in advance!
/Thomas

Would the jQuery .queue() function help you?

Could you store a sequencer variable that is an array (which you would be able to change) and then call a sequencer at the end of each function?
You could then pass a step code through each function and cross-reference that with the sequencer variable as to what the next step should be.
Pseudo Code:
var func['1'] = function(arg1,arg2,seq) {
//code
sequencer(seq);
}
var func['2'] = function(arg1,arg2,seq) {
//code
sequencer(seq);
}
var func['3'] = function(arg1,arg2,seq) {
//code
sequencer(seq);
}
var func['4'] = function(arg1,arg2,seq) {
//code
sequencer(seq);
}
function sequencer(seq) {
seq = seq + 1;
window.func[seq]
}

I tried executing this code:
var seq = 0;
var func = [];
func[1] = function(seq) {
setTimeout(function() {
console.log("Executing function 1");
sequencer(seq);
}, 2000);
}
func[2] = function(seq) {
console.log("Executing function 2");
sequencer(seq);
}
func[3] = function(seq) {
console.log("Executing function 3");
}
function sequencer(seq) {
seq = seq + 1;
func[seq].call();
}
sequencer(seq);
But the result (in Firebug) is:
Executing function 1
func[seq] is undefined
[Break on this error] func[seq].call();
I think that the problem is caused by context, but I'm not sure. JavaScript is sensitive to the context in which a function is called.
/Thomas

I found that what I was trying to achieve was slightly overkill for my purposes. So I decided to go with a different approach. I can send one or more boolean variables as a parameters to a function and use them to decide whether to execute a second function or not. Here's an example:
$("#justOneStep").click(function() {
loadImage(false);
});
$("#twoStepsPlease").click(function() {
loadImage(true);
});
function loadImage(boolDoMore) {
// Do the stuff that loads an image
...
if(boolDoMore) {
nextFunction();
}
}
function nextFunction() {
// Do some more stuff
...
}
Not very fancy but easy to understand and control and sufficient for my needs at the moment.
/Thomas

Binding multiple events of the same type?

Firstly, is it possible? Been struggling with this one for hours; I think the reason my events aren't firing is because one event is unbinding/overwriting the other. I want to bind two change events to the same element. How can I do that?
As per request, here's the function I'm struggling with:
(function($) {
$.fn.cascade = function(name, trigger, url) {
var cache = {};
var queue = {};
this.each(function() {
var $input = $(this);
var $trigger = $input.closest('tr').prev('tr').find(trigger);
//$input.hide();
var addOptions = function($select, options) {
$select.append('<option value="">- Select -</option>');
for(var i in options) {
$select.append('<option value="{0}">{1}</option>'.format(options[i][0], options[i][1]));
}
$select.val($input.val()).trigger('change');
}
var $select = $('<select>')
// copy classes
.attr('class', $input.attr('class'))
// update hidden input
.bind('change', function() {
$input.val($(this).val());
})
// save data for chaining
.data('name', name)
.data('trigger', $trigger);
$input.after($select);
$trigger.bind('change', function() {
var value = $(this).val();
$select.empty();
if(value == '' || value == null) {
$select.trigger('change');
return;
}
// TODO: cache should be a jagged multi-dimensional array for nested triggers
if(value in cache) {
addOptions($select, cache[value]);
} else if(value in queue) {
$select.addClass('loading');
queue[value].push($select);
} else {
var getDict = {}
getDict[name] = value;
// TODO: use recursion to chain up more than one level of triggers
if($(this).data('trigger')) {
getDict[$(this).data('name')] = $(this).data('trigger').val();
}
$select.addClass('loading');
queue[value] = [$select];
$.getJSON(url, getDict, function(options) {
cache[value] = options;
while(queue[value].length > 0) {
var $select = queue[value].pop();
$select.removeClass('loading');
addOptions($select, options);
}
});
}
}).trigger('change');
});
return this;
}
})(jQuery);
The relevant chunk of HTML is even longer... but essentially it's a select box with a bunch of years, and then an <input> that gets (visibly) replaced with a <select> showing the vehicle makes for that year, and then another <input> that gets replaced with the models for that make/year.
Actually, it seems to be running pretty well now except for on page load. The initial values are getting wiped.
Solved the issue by pulling out that $select.bind() bit and making it live:
$('select.province').live('change', function() {
$(this).siblings('input.province').val($(this).val());
});
$('select.make').live('change', function() {
$(this).siblings('input.make').val($(this).val());
});
$('select.model').live('change', function() {
$(this).siblings('input.model').val($(this).val());
});
Sucks that it's hard-coded in there for my individual cases though. Ideally, I'd like to encapsulate all the logic in that function. So that I can just have
$('input.province').cascade('country', 'select.country', '/get-provinces.json');
$('input.make').cascade('year', 'select.year', '/get-makes.json');
$('input.model').cascade('make', 'select.make', '/get-models.json');

Yes that is possible.
$(…).change(function () { /* fn1 */ })
.change(function () { /* fn2 */ });
jQuery event binding is additive, calling .change a second time does not remove the original event handler.

Ryan is correct in jQuery being additive, although if you find there are problems because you are chaining the same event, beautiful jQuery allows another approach, and that is calling the second function within the first after completion of the first as shown below.
$('input:checkbox').change(function() {
// Do thing #1.; <-- don't forget your semi-colon here
(function() {
// Do thing #2.
});
});
I use this technique frequently with form validation, one function for checking and replacing disallowed characters input, and the second for running a regex on the results of the parent function.
Update to Post:
OK... You all are quick to beat on me with your negative scores, without understanding the difference in how we each view Mark's request. I will proceed to explain by example why my approach is the better one, as it allows for the greatest flexibility and control. I have thrown up a quick example at the link below. A picture's worth a 1000 words.
Nested Functions on One Event Trigger
This example shows how you can tie in three functions to just one change event, and also how the second and third functions can be controlled independently, even though they are still triggered by the parent change event. This also shows how programmatically the second and third functions can BOTH be tied into the same parent function trigger, yet respond either with or independently (see this by UNCHECKING the checkbox) of the parent function it is nested within.
$('#thecheckbox').change(function() {
$("#doOne").fadeIn();
if ($('#thecheckbox').attr('checked')) { doFunc2() }
else { doFunc3() };
function doFunc2() { $("#doTwo").fadeIn(); return true; }
function doFunc3() { $("#doTwo").fadeOut(); return true; }
$("#doThree").fadeIn();
});
I've included the third 'Do thing #3 in the example, to show how yet another event can follow the two nested functions as described earlier.
Forgive the earlier bad pseudocode originally posted first, as I always use ID's with my jQuery because of their ability to give everything an individual status to address with jQuery. I never use the 'input:checkbox' method in my own coding, as this relies on the 'type' attribute of an input statement, and therefore would require extra processing to isolate any desired checkbox if there is more than one checkbox in the document. Hopefully, the example will succeed at articulating what my comments here have not.

I am actually not sure exactly if you can bind two different change events. But, why not use logic to complete both events? For example...
$('input:checkbox').change(function() {
// Do thing #1.
// Do thing #2.
});
That way, you get the same benefit. Now, if there are two different things you need to do, you may need to use logic so that only one or the other thing happens, but I think you would have to do that anyway, even if you can bind two change events to the same element.

Why is 'this' not updating to refer to a new object?

I'm writing an online game which allows a user to progress from one puzzle to the next, and if the user makes mistakes, each puzzle has a start again button to allow the user to start just that puzzle from scratch. A simplified version of the code's structure is below:
function puzzle(generator) {
this.init = function() {
this.generator = generator;
...
this.addListeners();
}
//fires when the puzzle is solved
this.completed = function() {
window.theSequence.next();
}
this.empty = function() {
//get rid of all dom elements, all event listeners, and set all object properties to null;
}
this.addListeners = function() {
$('#startOver').click(function() {
window.thePuzzle.empty();
window.thePuzzle.init();
});
}
this.init();
}
function puzzleSequence(sequenceGenerator) {
this.init = function() {
//load the first puzzle
window.thePuzzle = new puzzle({generating json});
}
this.next = function() {
//destroy the last puzzle and create a new one
window.thePuzzle.empty();
window.thePuzzle = new puzzle({2nd generating json});
}
}
window.theSequence = new puzzleSequence({a sequence generator JSON});
The problem I have is that if the user has progressed to the second puzzle, if they click start over it loads the first puzzle rather than the second. After a bit of debugging I've worked out that 'this', when used in methods by the second puzzle, for some reason still holds a reference to the first puzzle, but 'window.thePuzzle' - which should be the same as this - correctly refers to the second puzzle.
Why is 'this' persisting in referrring to the first one?
Let me know if you need more code samples

$('#startOver').click(this.empty);
You've taken the empty method and detached it from this to pass as a plain unbound function to jQuery. When it gets called back, it will have no reference to the original value of this. In fact, when a function is called unbound, this will refer to window, so you'll be scribbling what you think are properties onto the globals.
JavaScript doesn't bind methods in the same way as other languages. See eg. this answer for an explanation of what it actually does. This confuses many people; personally I consider it one of JavaScript's worst flaws.

There is a very good (and clear) description of exactly how the this reference is treated in different contexts over at Quirksmode.