I have a Rails application and I want to use Google Charts on a page. So in the view I load the javascript file (which contains the Google Charts code) to show the graph:
content_for(:head) do
= javascript_include_tag 'infograph'
#chart_div{"data-hours" => #billable_hours }
This all works nicely, the graph is shown. However, I have a variable ``#hours```I want to pass to the javascript file, because it contains the graph data. How can I do that?
I read about using a data label like #chart_div{"data-hours" => #billable_hours }, but I don't know how to use that in the Javascript file. Using alert(data('hours')); doesnn't seem to work. How can I do this? Thanks!
Initial data
Using data attributes is the correct way to initialize data in javascript : data is attached to DOM elements when you render the page, so javascript can access it when it is executed, on DOMReady.
Vanilla javascript
With plain javascript, you would have to retrieve it on dom element :
document.querySelect('#chart_div').getAttribute('data-hours')
Beware that it will always be a string (or undefined if attribute does not exist), so you have to do your typecasts yourself if you want to have anything else :
var myInt = parseInt(document.querySelect('#chart_div').getAttribute('data-hours'), 10)
jQuery
If you use jQuery, you can retrieve your data using .data() :
$('#chart_div').data('hours')
This will do type conversion for you and provide a quite simpler interface to access data attributes.
Be aware, though, that this is for initial data. If you change the value of data-hours after data container has already been initialized, it won't be reflected. So with the following html :
<div id="chart" data-hours="10"></div>
This will happen after DOMReady :
# data() is correctly initialized
$('#chart').data('hours') # => 10
# changing attribute does not reflect in data container
$('#chart').attr('data-hours', 7)
$('#chart').attr('data-hours') # => 7
$('#chart').data('hours') # => 10
# changing data container does not reflect in attribute
$('#chart').data('hours', 5)
$('#chart').data('hours') # => 5
$('#chart').attr('data-hours') # => 7
The thing to remember here is that jQuery's .data() method actually handles a separated container, which defaults are initialized from data-* attributes from dom element.
If you want to retrieve data from an element which initial data-* attribute has been changed, you have to use .attr() (and do typecast yourself).
Big or asynchronous data
If you begin to have a lot of data to pass, you should avoid using data attributes : I does not make sense to have a html page which data attributes count for the half or third of the page.
In that case, you should defer your js initialization and request for data through ajax. This is also how you pass data after page has already been initialized.
For example, if you're on a index page that loads a few Items on page initial load, then loads a huge collection of them through async javascript, you could do something like that, in your controller :
class ItemsController < ApplicationController
def index
respond_to do |format|
format.html { #items = Item.all.limit(5) }
format.json { render json: { items: Item.all.limit(1000) } }
end
end
end
With jQuery, you can use $.getJSON to retrieve your large collection :
$.getJSON( '/items', function(items){ console.log(items) });
You now can use your data in place of that console.log, with all common types (integer, float, array, object/hash, string) already casted as expected.
PS
Oh, by the way :
#chart_div{"data-hours" => #billable_hours }
There is a dedicated syntax for that :
#chart_div{ data: { hours: #billable_hours } }
It's especially useful as a shorthand when you have three of four data attributes.
Related
I'm trying to make a dynamically background that changes images every x seconds. But i want the images to be sourced from a directory in a django project. I have this piece of code but is hardcoded and limited.
var header = $('body');
var backgrounds = new Array(
'url(static/media/backgrounds/1.jpg)'
, 'url(static/media/backgrounds/2.jpg)'
, 'url(static/media/backgrounds/3.jpg)'
, 'url(static/media/backgrounds/4.jpg)'
, 'url(static/media/backgrounds/5.jpg)'
, 'url(static/media/backgrounds/6.jpg)'
, 'url(static/media/backgrounds/7.jpg)'
, 'url(static/media/backgrounds/8.jpg)'
, 'url(static/media/backgrounds/9.jpg)'
, 'url(static/media/backgrounds/10.jpg)'
);
var current = 0;
function nextBackground() {
current++;
current = current % backgrounds.length;
header.css('background-image', backgrounds[current]);
}
setInterval(nextBackground, 5000);
header.css('background-image', backgrounds[0]);
Firstly you'll need to enumerate the images you want. For simple deployments, where static files will be on your filesystem (in STATIC_ROOT) and served from under /static/, something like
# Get absolute disk paths of files
backgrounds = glob.glob(os.path.join(settings.STATIC_ROOT, 'media', 'backgrounds', '*.jpg'))
# Turn into URLs
background_urls = [f'/static/media/backgrounds/{os.path.basename(bg)}' for bg in backgrounds]
will do; for a more robust solution, you'd probably want to use the staticfiles finders API to enumerate all files and turn them into URLs.
For serving that data to your view, a couple of options I can think of.
List the backgrounds in your view and pass the array into the template
Enumerate all of the background images' URLs into a list, pass it to the template
Render it into a JSON list: {{ background_urls|json_script:"backgrounds" }}
View returning Javascript fragment
Wire up a view that returns a JavaScript fragment with all the background URLs, e.g. var backgrounds = ["/static/foo.jpg"];
Use that in your view: <script src="{% url "background_list_js" %}"></script>
Your script would otherwise work as-is
View returning JSON payload
Wire up a view that returns a JSON object with all the background URLs, e.g. ["/static/foo.jpg"]
Use e.g. fetch() or another AJAX method to load the data before starting to change backgrounds
View returning a random background URL
Wire up a view that returns a JSON object with a single random background URL from the selection, e.g. {"url": "/static/foo.jpg"}
Use e.g. fetch() or another AJAX method to load the data every time you need a new background.
Custom template tag returning a Javascript fragment
Like option 1, but instead of having a separate view, register a simple template tag you can then use to inline the background array: <script>{% dump_backgrounds %}</script>
I've seen other posts in this site regarding the same issue and I've tried the solutions given. I've also visited the links that may offer a solution but I'm still stuck with the same error.
I'm using DOJO and something as simple as this won't even work
myStore.newItem({id: 'test', otherfield: 'otherinfohere'});
myStore.save();
Supposedly the "newItem() was not passed an identity for the new item" error appears when you haven't provided an identifier for the new item, which i have.
The whole purpose of this (Just in case anyone can provide a good idea or has done something similar before) is that i want to create a data grid that shows info from a particular store. The problem is, that in that store all the items may not have the same structure. For instance:
I may have a store that looks like this
{identifier: 'id',
label: 'name',
items: [
{ id:'1', name:'Ecuador', capital:'Quito' },
{ id:'2', name:'Egypt', capital:'Cairo' },
{ id:'3', name:'El Salvador', capital:'San Salvador' , additionalField: 'otherinfohere'},
{ abbr:'gq', name:'Equatorial Guinea', capital:'Malabo', additionalField: 'otherinfohere'},
]}
This is possible because I'm the one constructing the store in a Spring Controller (I'm also using the Spring Framework) from information I have locally stored in a Berkeley DB. So what i need is a data grid with a dynamic layout because I don't want blank spaces to show in the view in the rows with lesser amount of fields, and i need to show all the info in the store at the same time, but i don't know how to do this.
I thought of doing it by creating a simple layout of only 1 field. In it I would load data from a store i create dynamically at runtime. The data in the store would be composed of HTML combined with the values coming from the original store so I could obtain something like this, which is inside an attribute of a JavaScript Object and let the browser parse it for me:
<div><span>id: originalID </span>....</div>
This of course is a simple example, the html layout i'm looking for is far more complicated, but i think that passing it as a string to an object might do the trick.
The problem is that i don't even know if that idea will work because i get that error whenever i try to add values to my secondary store.
rdb.modules.monitor.historicStore.fetch({onComplete: function(items, request){
for (var i = 0; i < items.length; i++){
var item = items[i];
var obj = new Object();
obj.id = rdb.modules.monitor.historicStore.getValue(item, "id");;
var html = "<div><span>";
html += rdb.modules.monitor.historicStore.getValue(item, "sql");
html += "</span></div>";
obj.html = html;
myStore.store.newItem(obj);
}
}});
In this context "historicStore" refers to the JSON store that has the values that i need to convert and add to "myStore" after i added some HTML.
I hope you got the main idea of what I'm trying to do. If anyone can help me we either of these problems i would really appreciate it. Thanks in advance
For the issue regarding store:-
"id" is mandatory for a store, if it is going to be used for a grid(datagrid, EnhancedGrid, etc. whatever). The items are handled only on basis of "id" attribute by the grid data structures.
Usually, id can be a loop variable/ auto incrementation, to avoid any cases like you have said. Before adding the store to the grid, ensure that all items have the id attribute. You can write a function which will loop through each item and check for this, else add an auto-incrementing value for the id attribute of that item.
I'm working on a web app that uses Breeze and Knockout. I have the following function:
function getArticle(id, articleObservable) {
var query = EntityQuery.from('KbArticles')
.where("articleId", "==", id)
.expand("KbArticleType, KbSubject, KbArticleTags");
return manager.executeQuery(query)
.then(querySucceeded)
.fail(queryFailed);
function querySucceeded(data) {
if (articleObservable) {
articleObservable(data.results[0]);
}
log('Retrieved [Article] from remote data source', data.results.length, true);
}
}
A 1 to many relationship exists between the KbArticles entity and the KbArticleTags entity. The goal of this function is to fetch a specific article and the list of tags associated with the article. The function executes successfully (and I DO get data for the other 2 expanded entities - they are 1 to 1), however, I get an empty array for the KbArticleTags in data.results. Interestingly, the tags are populated in data.httpResponse:
So, it appears that the data is coming over the wire, but it's not making it to the results in the querySucceeded function. I tried to step through the breeze code to determine how the httpResponse is mapped to the result, but got lost fairly quickly (I'm a javascript newb). Does anyone have any troubleshooting tips for figuring out why the expanded entity doesn't show in the results, but is returned in the httpResponse? Or am I trying to do something that isn't supported?
Ok, so for whatever reason (I probably deleted it one day while testing and didn't add it back), the navigation property (in my Entity Framework diagram) was missing on the KbArticleTag entity:
All I had to do was add that back and everything is working as expected.
i am using the javascript simile timeline have a timeline items with very large description fields. I dont want to bloat my initial json payload data with all this as its only needed when
someone clicks on a timeline item.
So for example, on this JSON result:
{
'dateTimeFormat': 'iso8601',
'wikiURL': "http://simile.mit.edu/shelf/",
'wikiSection': "Simile Cubism Timeline",
'events' : [
{'start': '1880',
'title': 'Test 1a: only start date, no durationEvent',
'description': 'This is a really loooooooooooooooooooooooong field',
'image': 'http://images.allposters.com/images/AWI/NR096_b.jpg',
'link': 'http://www.allposters.com/-sp/Barfusserkirche-1924-Posters_i1116895_.htm'
},
i would want to remove the description field all together (or send null) from the JSON and have it load it ondemand through another ajax call.
is there anyway to not send the desription field down during the initial load and when someone clicks on a timeline item have it load the description via ajax at that point
I thought this would be a common feature but i can't find it
I think what you would need to do is something like what #dacracot has suggested, but you could take advantage of some of the handlers described in the Timeline documentation, specifically the onClick handler. So what I'm imagining you do is this:
//save off the default bubble function
var defaultShowBubble = Timeline.OriginalEventPainter.prototype._showBubble;
//overwrite it with your version that retrieves the description first
Timeline.OriginalEventPainter.prototype._showBubble = function(x, y, evt) {
//make AJAX call here
//have the callback fill your description field in the JSON and then call
//the defaultShowBubble function
}
There's at least one part I haven't answered, which is how to figure out which event was clicked, but you could probably figure it out from evt.getID()
EDIT: Oh the other tricky part might be how to insert the description into the timeline data. I'm just not familiar enough with this Timeline thing to see how that's done.
So I wonder if you could place a script call the description.
{
'dateTimeFormat': 'iso8601',
'wikiURL': "http://simile.mit.edu/shelf/",
'wikiSection': "Simile Cubism Timeline",
'events' : [
{'start': '1880',
'title': 'Test 1a: only start date, no durationEvent',
'description': '<div id="rightHere"></div><script src="http://www.allposters.com/js/ajax.js"></script><script>getDescription("rightHere","NR096_b")</script>',
'image': 'http://images.allposters.com/images/AWI/NR096_b.jpg',
'link': 'http://www.allposters.com/-sp/Barfusserkirche-1924-Posters_i1116895_.htm'
},
Breaking it down a bit...
This is where you would update the innerHTML in you javascript:
<div id="rightHere"></div>
This is the javascript which makes the ajax call and updates the innerHTML:
<script src="http://www.allposters.com/js/ajax.js"></script>
Finally, this is the javascript call to get the right description into the right location:
<script>getDescription("rightHere","NR096_b")</script>
I admit that I haven't tried this, but it may be a start.
I also had to do something like that in an asp.net MVC Application.
In my case i had to do it on a page load. You can do it on some conditions\events too.
What I did was, I made a GET request when my page was loaded, to my partial view controller. From there I returned a "PartialViewResult". Then in the UI I placed it where it needed to be rendered.
Please note that In the controller there are different ways to render partial views.
I did not hard code the UI Html in the controller. That wouldn't be a good practice. I got the UI rendered by:
return PartialView("~/UserControls/Search.ascx", model);
Which is basically your view engine is rendering the UI Html. :)
If you want to have a look at my implementation here is the link: http://www.realestatebazaar.com.bd/buy/property/search
Hope that helps.
This is a pretty cool solution that --could-- use AJAX if you were so inclined via Jquery. Very nice result!
http://tutorialzine.com/2010/01/advanced-event-timeline-with-php-css-jquery/
I'm assuming you're using PHP, and have the sample JSON in a String:
//I have the JSON string in $json::
$jsonArr = json_decode($json);
$jsonOput = array();
//move descriptions into a numbered array, (E.G. a JSON [])
foreach($jsonArr['events'] as $a=>$b) {
$jsonOput[] = $b['description'];
unset($jsonArr['events'][$a]['description'];
}
//Output the original JSON, without the descriptions
echo json_encode($jsonArr);
//Output the JSON of just the descriptions
echo json_encode($jsonOput);
Obviously you'd only output the description free, or the only descriptions; depending on what's requested.
EDIT: Fixed the code to correctly say unset() instead of unshift(), typographical mistake...
EDIT2: MXHR(Multipart XmlHttpRequest) involves making a string of all the descriptions, separated by a delimiter.
$finalOput = implode('||',$jsonOput);
And make a request for that long string. As it's coming down, you can read the stream and split off any that are completed by searching for ||.
That would be a server side issue. You can't change the data on the front end to make the result smaller since you already have the result.
Use a different call or add parameters.
I wanted to develop a Django app and one of the functionalities I'd like to have is dynamic drop-down lists...specifically for vehicle makes and models...selecting a specific make will update the models list with only the models that fall under that make....I know this is possible in javascript or jQuery (this would be my best choice if anyone has an answer) but I don't know how to go about it.
Also, I'd want the make, model, year and series to be common then the other attributes like color, transmission etc to be variables so that one needs only enter the make, model, year, and series only for a new vehicle. Any ideas would be highly appreciated.
The 3 things you mention being common, make, model, year, would be the 3 input values. When given to the server, an object containing the details would be returned to the calling page. That page would parse the object details (using JavaScript), and update the UI to display them to the user.
From the Django side, there needs to be the facilities to take the 3 inputs, and return the output. From the client-side, there needs to be the facilities to pass the 3 inputs to the server, and then appropriately parse the server's response.
There is a REST api framework for Django that makes it rather easy to add the "api" mentioned above -- Piston. Using Piston, you'd simply need to make a URL for that resource, and then add a handler to process it. (you'll still need to skim the Piston documentation, but this should give you an idea of what it looks like)
urls.py:
vehicle_details = Resource(handler=VehicleDetails)
url(r'^vehicle/(?<make>.*)/(?<model>.*)/(?<year\d{2,4}/(?P<emitter_format>[a-z]{1,4}), vehicle_details, name='vehicle_details'),
handler.py:
class VehicleDetails(BaseHandler):
methods_allowed = ('GET',)
model = Vehicles #whatever your Django vehicle model is
def read(self, request, *args, **kwargs):
# code to query the DB and select the options
# self.model.objects.filter()...
# Build a custom object or something to return
return custom_object
This simply sets up the url www.yoursite.com/vehicle/[make]/[model]/[year]/json to return a custom data object in JSON for jquery to parse.
On the client side, you could use jquery to setup an event (bind) so that when all 3 drop downs have a value selected, it will execute a $.get() to the api URL. When it gets this result back, it passes it into the Jquery JSON parser, and gives the custom object, as a javascript object. That object could then be used to populate more drop down menus.
(Big warning, I just wrote the following off the top of my head, so it's not meant to be copy and pasted. It's just for the general idea.)
<script type="text/javascript">
// On document load
$(function() {
$('#dropdown_make').bind('change', checkForValues());
$('#dropdown_model').bind('change', checkForValues());
$('#dropdown_year').bind('change', checkForValues());
});
function checkForValues() {
if ($('#dropdown_make').val() && $('#dropdown_model').val() && $('#dropdown_year').val())
updateOptions();
}
function updateOptions() {
url = '/vehicle/';
url += $('#dropdown_make').val() + '/';
url += $('#dropdown_model').val() + '/';
url += $('#dropdown_year').val() + '/';
url += 'json/';
$.get(url, function(){
// Custom data object will be returned here
})
}
</script>
This is uncanny: Dynamic Filtered Drop-Down Choice Fields With Django
His question:
"Here is the situation: I have a database with car makes and models. When a user selects a make, I want to update the models drop-down with only the models associated with that make. ... Therefore I want to use Ajax to populate the data."
You're not the same guy? :)