I want to track a variable as I navigate around my site. How can I use jQuery to output this value without having to worry about tracking down wherever it might be affected and having it update.
var num = 1;
$(#trackvariable).text(num)
I want the above to execute constantly as it were.. I don't necessarily want to do it on a timer. Is there any way to do that?
If you want to listen to changes on a textnode, you can do something like this:
function InitListener () {
var container = document.getElementById ("textContainer");
var textNode = container.firstChild;
if (textNode.addEventListener) {
textNode.addEventListener ('DOMCharacterDataModified', OnCharacterModified, false);
}
}
This will only work in Firefox (and probably Chrome in Safari also):
https://developer.mozilla.org/en/JavaScript/Guide/Working_with_Objects#Defining_Getters_and_Setters
Off the top of my head I would say that the functions changing the variable should just call some sort of update function at the end of them? just an idea. I think even if you set up some kind of custom event it would still have to manually triggered in each function.
Related
I would like to be able to use the dc.js select menu (dc.selectMenu) in such a way that when I click on an element it gets the value of said element and that becomes the value of the select, once selected it should refresh the data as it normally would if you had just selected in the first place.
The problem I'm having is that I can set the value, but dc.redrawAll() seems to do nothing for me so I think I must be filtering wrongly, but I can't find much information online regarding how to do it other than simply using the filter method (not onclick).
I have tried to set the destination to whatever data-destination is which appears to be working, the value of the select does update when I check with console.log to check the value of the select menu, I then use the dc.redrawAll() function expecting it would filter based on the select option but it does nothing (not even an error in the console)
My function so far is looking like:
function select_destination(ndx) {
var destination_dim = ndx.dimension(dc.pluck('destination'));
var destination_group = destination_dim.group();
var destination = null;
document.addEventListener('click', function(e) {
if (!e.target.matches('.open-popup-link')) return;
e.preventDefault();
var destination = e.target.getAttribute('data-destination').toString();
document.getElementById('select-destination').value = destination;
dc.redrawAll();
});
dc.selectMenu('#select-destination')
.dimension(destination_dim)
.group(destination_group)
.filter(destination);
}
I would expect the graphs to update based on the select option but nothing happens, and I get no error message to go off either.
I suspect I'm using dc.redrawAll() wrongly as if I go to the console and type dc.redrawAll(); I get undefined but I'm really at a loss now and the documentation isn't really helping me at this point so I don't know what else to do.
they are bits of your code that I don't quite understand, for instance why do you have have filter(destination /*=null */)
anyway, So you want to filter the select menu? you can call directly the replaceFilter function with the value, as done in the source code:
menu.replaceFilter(destination);
dc.events.trigger(function () {
menu.redrawGroup();
});
See the source code for the full example of how it's done
https://dc-js.github.io/dc.js/docs/html/select-menu.js.html#sunlight-1-line-129
as for why it doesn't work, I have had some surprising results mixing d3 with pure dom js. Try to rewrite your even handler in d3, eg
d3.select('#select-destination').property('value', destination);
it's possibly that changing the value on the dom directly isn't triggering the change event.
My experience with d3 is that it works better to change the underlying data (call directly filter functions or whatever you want to do) and let dc redraw the needed rather than manipulating the dom directly
I need to be able to change some variable's value, when app is closed.
I'm using exitEvent described here:
https://docs.nativescript.org/core-concepts/application-lifecycle
Also, i'm using local-storage plugin that works similar to javasctip's localstorage.
https://github.com/NathanaelA/nativescript-localstorage
My simple code looks like this:
var Observable = require("data/observable").Observable;
require("nativescript-dom");
var LS = require("nativescript-localstorage");
const application = require("tns-core-modules/application");
var page = require("ui/page");
exports.load = function (args) {
var page = args.object;
var model = new Observable();
var frame = require('ui/frame');
var ff = frame.getFrameById("dashboard");
var topmost = frame.topmost();
// This is exit event
application.on(application.exitEvent, (args) => {
LS.setItem('XX','111')
});
// What i will exit app, and run app again this will newer become 111,
it's null all the time
console.log(LS.getItem('XX'));
}
So, my question is - is possible to set any flag on app exit - it do not have to be localstorage (i've tested global variables to), to detect if exit was made, and based on this i can make a decisions that will help me ?
One of scenarios may be - i'm holding some flag in Localstorage that is TURE is user tapped "rememebr me" on the login screen.
So on exit i can check if he want's to be rememebered, if not i want to send user to login page and not dashboard when app is lauching....
Thank you.
EDIT:
I've tried applications-settings too, it will not work.
application.on(application.exitEvent, (args) => {
applicationSettings.setString("Name", "John Doe");
});
console.log(applicationSettings.getString("Name")); // not working
I suspect it's the issue with the nativescript-localstorage plugin. It writes the changes to file after a 250ms delay. At exit event you will give you very limited amount of time before your app is completely killed by system.
May be the Author had a reason for setting up this delay but I think its too much of time at least in this particular scenario so the changes are never written to file. You may raise a issue at the plugin's Github repo.
If you are looking for an immediate workaround, copy localstorage.js to your app and export internalSaveData from the file, so you could directly call it right after you finish setting your values.
I'm using leaflet-ajax to load geoJSON on demand. I want to find the maximum theProperty value so I can use that to scale the feature's fill colors before I add them to the map.
Here's my general approach:
function maxBinPropertyValue(theProperty) {
var theGeoJson = null;
var maxPropertyValue = 0;
var propertyValue = null;
var theGeoJson = new L.GeoJSON.AJAX(binsFileName());
theGeoJson.on('data:loaded', function() {
console.log('The data is loaded');
theGeoJson.eachLayer(function(layer) {
console.log('Looping through the layers');
propertyValue = feature.properties[theProperty];
if (propertyValue > maxPropertyValue) {
maxPropertyValue = propertyValue;
console.log('Max so far: ' + maxPropertyValue);
};
});
});
theGeoJson = null;
console.log('The final maximum value: ' + maxPropertyValue);
return maxPropertyValue;
};
I'm trying to wait for the data:loaded event, then loop through all the features to find the maximum value of theProperty, which is returned to the calling routine.
Except it doesn't work. The first console.log says 'The data is loaded'. The second and third console.logs are never reached, and the fourth and final one reports a value of 0 for maxPropertyValue.
How can I examine all the features in a featureset before styling them, in a way guaranteed to not have asynchronous problems?
PS: I'm pretty sure I can't use onEachFeature: instead of the above approach, because I need to examine every feature's property to determine the maximum value in the set before I can style any of the features.
As for your issue about inspecting your data and retrieving the maximum value, you are indeed facing the classic asynchronous concept of JavaScript.
See How do I return the response from an asynchronous call?
Asynchronism is a problem if not dealt with properly, but an advantage if correctly handled.
To put the concept shortly, you do not manage asynchronism in a "standard" sequential way, but you should rather consider parts of code (callbacks) that are executed at a later time based on events.
Whenever you provide a function as an argument, it is certainly a callback that will be executed at a later time, but very probably much later than the next instructions.
So in your case, your 2nd and 3rd console.log are within a callback, and will be executed once your data is loaded, which will happen much later than your 4th console.log.
As for your next step (styling and adding to map), you actually do not need to perform an extra AJAX call, since you already have all data available in theGeoJson variable. You simply need to refactor / restyle it properly.
It is a good approach to break your problem in small steps indeed.
Good luck!
PS: that being said, ES7 provides async and await functionalities that will emulate a sequential execution for asynchronous functions. But to be able to use those, you need latest browser versions or transpilation, which is probably more work to learn and configure as of today for a beginner than understanding how to work with async JS.
I also had this problem and had to wrap my head around this, so giving an explicit example for solution here;
// make a request with your "url"
var geojsonLayer = new L.GeoJSON.AJAX("url");
// define your functions to interact with data
function thingToDoBeforeLoadingStarts () {
// do stuff
}
function thingToDoForEachFileDownloaded () {
// do stuff
}
function thingToDoAfterAllDownloadEnds () {
// do stuff
}
// attach listeners
geojsonlayer.on("data:loading",thingToDoBeforeLoadingStarts);
geojsonLayer.on("data:progress",thingToDoForEachFileDownloaded)
geojsonLayer.on("data:loaded",thingToDoAfterAllDownloadEnds);
I've got a few event listeners than i need to able to remove once they are no longer needed.
I've followed the advice of a few others and included the RemoveEventListener inside the function itself like:
object1.addEventListener(MouseEvent.MOUSE_DOWN, function StartMove(event:MouseEvent):void
{
mousePoint = new Point(MC.mouseX, MC.mouseY);
objectOffset = new Point(int(mousePoint.x - object1.x), int(mousePoint.y - object1.y));
mousePoint.y -= objectOffset.y;
mousePoint.x -= objectOffset.x;
mousePressed = true;
event.currentTarget.removeEventListener(event.type, StartMove);
});
but this simply creates the listener and then deletes it when its used once.
The event listener functions are created inside a larger function (MouseMoves()) as they make use of local variables within MouseMoves(). (not sure whether this is an appropriate way to do this.)
So if i try to remove the listeners externally they cant see the function name to remove, and i cant declare the functions outside MouseMoves() cus they use variables inside it.
feel like this is bad design on my part but i'm not sure where?
is there a 'proper' more standard way to remove an event listener?
thanks.
When you ready to have you event listener removed you could use the same syntax that you used to add it in the first place. So somewhere in your code when you're ready to remove this listener you could have this
object1.removeEventListener(MouseEvent.MOUSE_DOWN, function StartMove(event:MouseEvent):void
This way your being specific about which object you want to remove the listener from.
Your mouse function would look like this:
object1.addEventListener(MouseEvent.MOUSE_DOWN, function StartMove(event:MouseEvent):void
{
mousePoint = new Point(MC.mouseX, MC.mouseY);
objectOffset = new Point(int(mousePoint.x - object1.x), int(mousePoint.y - object1.y));
mousePoint.y -= objectOffset.y;
mousePoint.x -= objectOffset.x;
mousePressed = true;
});
Yes, your coding of:
event.currentTarget.removeEventListener(event.type, StartMove);
can be used without problem in the StartMove function. It is just to unregister the event in the listener, don't worry if it is in the event function. And of course you can also use:
object1.removeEventListener(MouseEvent.MOUSE_DOWN, StartMove);
in the StartMove function as well if you do not want to use event.currentTarget.removeEventListener.
I am using the file.saveURL in a loop and its working good but I am seeing some strage things. Basically I loop over about 70 images and then grab the uri to them after they are saved and store that locally so I can then use it to display in the app
What happens is that once the loop is done I display the images out but randomly some of the images are the same. I have validated the correct URL is being passed but its as if and I don't know for sure but maybe the function is not done with the previous and is somehow overwriting it?
This makes the most sence because the issue usually happens with images right next to each other.
So I guess my question is, does the file.saveURL only work on a one to one aspect, like it has to by synchronous?
If that is the case what would be the recommended approach for looping over and saving these images.
Thanks!
EDIT
This is a basic sample (I have some conditional stuff in there but this is the main part)
I have the JSON object stored and I loop over it
$(data).each(function(i){
var slcval = 'speaker' + this.SID;
var imageID = 'simageid' + this.IMAGE;
var speakerImage = "http://mydomain.com/users/images/speakers/" + this.IMAGE;
//then I call the save url function
saveURLImage(speakerImage,slcval,'speaker',this.SID,imageID);
}
this loops over my images and calls the save image function that then does the save URL function
function saveURLImage(url,ID,type,extraVal,imageID){
forge.file.saveURL(url, function (file) {
forge.file.URL(file, function (url) {
var fileObject = JSON.stringify(url);
localStorage.setItem(ID, fileObject);
})
});
}
This is a simple version of it, I have some other parts that set some localstorage vars but this is the main call.
So my problem was a scoping issue
so if anyone else comes arrocss this I found this thred that helped out
Javascript: function in setTimeout and references
Basically what I did was creat a function that has an announmous function in it so the scope would be correct
function saveURLImage(url,ID,type,extraVal,imageID) {
(function() {
saveURLImageScoped(url,ID,type,extraVal,imageID)
})();
}
so the function name is still the same as before but I renamed the main function saveURLImageScoped and now it has its own variable scope