We use DNN and often need to pass a few context specific values (like page id or module-on-page-id) into an AngularJS app. We've developed our own conventions how to do this, but would like to hear from others how they approach this to find a best practice.
So basically the situation is that the server-page has information needed by the JS. Using WebAPI is not an option, as these values are known in the page, but not in a separate request. Things I've seen so far have been:
Use in-view-razor like href="#Tab.TabId/{{...}}" (I don't like this)
Place the values in the ng-init like ng-init="config = { prop1: '#Tab.TabId' }"
Create a separate <script> tag where we generate a module on the fly containing these values so angular.module("config", []).constant('prop1', '#Tab.TabId')
Create a json with razor in the page somewhere and inject all of it as a module into the app using a generic code which does the same as #3, just with cleaner code re-use.
I've seen all these and have also used all. Currently we avoid #1 as we believe it's not good to mix templating languages and because it doesn't allow externalizing parts of the view. So basically we use #2 as for quick-and-simple (and a bit dirty) + #3/#4 for larger projects.
Do you have a better way, or which way would you prefer?
We are using variant #4.
This has the advantage that the JSON defines the exact interface for the config needed by the JS module. And Razor is great to generate URLs using #Url.Action.
we use NewtonSoft and do JSONConvert.SerializeObject(ObjectName) and then pass it over as a Session from the controller and then use #Html.Raw(ObjectName) and its a JSON Object that can be utilized easily in javascript...
What I'm trying to do is offer search functionality on a webpage where all data is displayed when loading the page. The dataset is not very large (think <500 items) so it would be very user-friendly to offer some search functionality that does not require a page refresh (or any requests for that matter). I've looked at some interesting Javascript libraries (summed up in this answer), and especially Fuse.js and Lunr.js look very suitable for my scenario.
The problem is that I don't know how to apply these libraries -- which seem to search through JSON exclusively -- to the context passed by Django. I have only scratched the surface of the functionality of Django, because I've only started working on it a few days ago, so pardon me if I'm missing something obvious. Thank you!
You just need to output the JSON in your template. You can either pass it directly from your view via json.dumps(), or manually iterate through the data in your template to create the JSON. The first would be preferable.
So, using the Fuse example, your view would do:
def my_view(request):
data = ... get data from wherever ...
return render(request, 'template.html', {"data": json.dumps(data)})
and the template:
<script type="text/javascript">
var data = {{ json_data }}
var options = ...
var f = new Fuse(data, options)
</script>
While Daniel (in the comments) is certainly correct for telling me how to add JSON to the context - I probably should have phrased the question differently. But I digress.
After some more work I am now generating a correct JSON from the object hierarchy. This JSON is passed through the context, and is then used together with Mustache.js to generate HTML. I could not figure out a way to pass data as JSON and also use Django's templating language to iterate through the JSON. When approaching this from the other direction, I could not figure out a way to convert the regular Django context (e.g. a context with var.objects.all()) to JSON on the client-side (because of some silly nonsense with single-quotes..)
Nevertheless generating HTML with Mustache.js was not so bad after all, because this allowed me to easily manipulate the page with the search results generated by the search algorithm (in my case Fuse.js). Hopefully the performance will be al right in production, but it certainly looks very promising!
I am using C# to create a rather complicated data object that contains a couple of lists of objects that is then serialized and sent to the client. I like this approach a lot because I am using the same object definition in both my client and server side code.
I'd like to create some sort of reference file for Visual Studio 2012 so that intellisense can help me out, typos in my javascript code seem to be my biggest problem in debugging.
Does anybody have any tips for doing this? I understand that as I add new properties to the C# class I will need to refresh this reference file.
You can use T4 template to generate javascipt viewmodel file from your C# class.
Take a look at this article.
Also some more information available.
I'm trying to wrap my head around Node.js streams, not that I'm pretty new to JavaScript and node, the last languages I really got were Perl and PHP :-D
I've read the Buffer/Streams documentation # nodejs.org, watched James Halliday # LXJS, read his stream-handbook and Thorsten Lorenz event-stream post. I start to understand the basics :)
I process data which is serialized in RDF (which is neither JSON nor XML). I manage to fetch the data (in real code via request) and parse it into a JS object using rdfstore module.
So far I do this:
s.createReadStream('myRDFdata.ttl').pipe(serialize()).pipe(process.stdout);
Where serialize()does the job of parsing an serializing the code at the same time right now. I use through module to interface to the stream.
Now I have some more methods (not the real function declaration but I hope you get the point):
getRecipe(parsedRDF) -> takes the parsed RDF (as a JavaScript object) and tells me how to use it
createMeal(parsedRDF, recipe) -> takes the parsed RDF and the recipe from above and creates a new RDF object out of it
this new object needs to get serialized and sent to the browser
(In the real world getRecipe will have to do a user interaction in the browser)
I like the idea of chaining this together via pipes for higher flexibility when I enhance the code later. But I don't want to serialize it to a RDF serialization every time but just send around the JS object. From what I've read in the documentation I could use the stringify module to get a string out of each step for piping it to the next step. But:
does this actually make sense? In terms of do I add unnecessary overhead or is this negligible?
I don't see how I could give the parsedRDF to both methods with the dependency that getRecipe would have to be called first and the output is input for createMeal as well. Are there modules which help me on that?
It might be that I have to ask the user for the final recipe selection so I might need to send stuff to the browser there to get the final answer. Can I do something like this over sockets while the pipe is "waiting"?
I hope this shows what I'm trying to do, if not I will try to give more details/rephrase.
Update: After sleeping over it I figured out some more things:
It probably doesn't make sense to serialize a format like RDF into something non-standard if there are official serialization formats. So instead of using stringify I will simply pass an official RDF serialization between the steps
This does imply that I parse/serialize the objects in each step and this surely does add overhead. Question is do I care? I could extend the RDF module I use to parse from stream and serialize into one
I can solve the problem with the dependency between getRecipe and createMeal by simply adding some information from getRecipe to parseRDF, this can be done very easily with RDF without breaking the original data model. But I would still be interested to know if I could handle dependencies like this with pipes
yes, It's okay to make a stream of js objects,
you just have to remember to pipe it through something that will serialize the stream again after before writing it to IO.
I'd recomend writing a module called rdfStream that parses and serializes rdf, you would use it like this
var rdf = require('rdf-stream')
fs.createReadStream(file) //get a text stream
.pipe(rdf.parse()) //turn it into objects
.pipe(transform) //optional, do something with the objects
.pipe(rdf.stringify()) //turn back into text
.pipe(process.stdout) //write to IO.
and it could also be used by other people working with rdf in node, awesome!
I'm using Django and Apache to serve webpages. My JavaScript code currently includes a data object with values to be displayed in various HTML widgets based on the user's selection from a menu of choices. I want to derive these data from a Python dictionary. I think I know how to embed the JavaScript code in the HTML, but how do I embed the data object in that script (on the fly) so the script's functions can use it?
Put another way, I want to create a JavaScript object or array from a Python dictionary, then insert that object into the JavaScript code, and then insert that JavaScript code into the HTML.
I suppose this structure (e.g., data embedded in variables in the JavaScript code) is suboptimal, but as a newbie I don't know the alternatives. I've seen write-ups of Django serialization functions, but these don't help me until I can get the data into my JavaScript code in the first place.
I'm not (yet) using a JavaScript library like jQuery.
n.b. see 2018 update at the bottom
I recommend against putting much JavaScript in your Django templates - it tends to be hard to write and debug, particularly as your project expands. Instead, try writing all of your JavaScript in a separate script file which your template loads and simply including just a JSON data object in the template. This allows you to do things like run your entire JavaScript app through something like JSLint, minify it, etc. and you can test it with a static HTML file without any dependencies on your Django app. Using a library like simplejson also saves you the time spent writing tedious serialization code.
If you aren't assuming that you're building an AJAX app this might simply be done like this:
In the view:
from django.utils import simplejson
def view(request, …):
js_data = simplejson.dumps(my_dict)
…
render_template_to_response("my_template.html", {"my_data": js_data, …})
In the template:
<script type="text/javascript">
data_from_django = {{ my_data }};
widget.init(data_from_django);
</script>
Note that the type of data matters: if my_data is a simple number or a string from a controlled source which doesn't contain HTML, such as a formatted date, no special handling is required. If it's possible to have untrusted data provided by a user you will need to sanitize it using something like the escape or escapejs filters and ensure that your JavaScript handles the data safely to avoid cross-site scripting attacks.
As far as dates go, you might also want to think about how you pass dates around. I've almost always found it easiest to pass them as Unix timestamps:
In Django:
time_t = time.mktime(my_date.timetuple())
In JavaScript, assuming you've done something like time_t = {{ time_t }} with the results of the snippet above:
my_date = new Date();
my_date.setTime(time_t*1000);
Finally, pay attention to UTC - you'll want to have the Python and Django date functions exchange data in UTC to avoid embarrassing shifts from the user's local time.
EDIT : Note that the setTime in javascript is in millisecond whereas the output of time.mktime is seconds. That's why we need to multiply by 1000
2018 Update: I still like JSON for complex values but in the intervening decade the HTML5 data API has attained near universal browser support and it's very convenient for passing simple (non-list/dict) values around, especially if you might want to have CSS rules apply based on those values and you don't care about unsupported versions of Internet Explorer.
<div id="my-widget" data-view-mode="tabular">…</div>
let myWidget = document.getElementById("my-widget");
console.log(myWidget.dataset.viewMode); // Prints tabular
somethingElse.addEventListener('click', evt => {
myWidget.dataset.viewMode = "list";
});
This is a neat way to expose data to CSS if you want to set the initial view state in your Django template and have it automatically update when JavaScript updates the data- attribute. I use this for things like hiding a progress widget until the user selects something to process or to conditionally show/hide errors based on fetch outcomes or even something like displaying an active record count using CSS like #some-element::after { content: attr(data-active-transfers); }.
For anyone who might be having a problems with this, be sure you are rendering your json object under safe mode in the template. You can manually set this like this
<script type="text/javascript">
data_from_django = {{ my_data|safe }};
widget.init(data_from_django);
</script>
As of mid-2018 the simplest approach is to use Python's JSON module, simplejson is now deprecated. Beware, that as #wilblack mentions you need to prevent Django's autoescaping either using safe filter or autoescape tag with an off option. In both cases in the view you add the contents of the dictionary to the context
viewset.py
import json
def get_context_data(self, **kwargs):
context['my_dictionary'] = json.dumps(self.object.mydict)
and then in the template you add as #wilblack suggested:
template.html
<script>
my_data = {{ my_dictionary|safe }};
</script>
Security warning:
json.dumps does not escape forward slashes: an attack is {'</script><script>alert(123);</script>': ''}. Same issue as in other answers. Added another answer hopefully fixing it.
You can include <script> tags inside your .html templates, and then build your data structures however is convenient for you. The template language isn't only for HTML, it can also do Javascript object literals.
And Paul is right: it might be best to use a json module to create a JSON string, then insert that string into the template. That will handle the quoting issues best, and deal with deep structures with ease.
It is suboptimal. Have you considered passing your data as JSON using django's built in serializer for that?
See the related response to this question. One option is to use jsonpickle to serialize between Python objects and JSON/Javascript objects. It wraps simplejson and handles things that are typically not accepted by simplejson.
Putting Java Script embedded into Django template is rather always bad idea.
Rather, because there are some exceptions from this rule.
Everything depends on the your Java Script code site and functionality.
It is better to have seperately static files, like JS, but the problem is that every seperate file needs another connect/GET/request/response mechanism. Sometimes for small one, two liners code os JS to put this into template, bun then use django templatetags mechanism - you can use is in other templates ;)
About objects - the same. If your site has AJAX construction/web2.0 like favour - you can achieve very good effect putting some count/math operation onto client side. If objects are small - embedded into template, if large - response them in another connection to avoid hangind page for user.
Fixing the security hole in the answers by #willblack and #Daniel_Kislyuk.
If the data is untrusted, you cannot just do
viewset.py
def get_context_data(self, **kwargs):
context['my_dictionary'] = json.dumps(self.object.mydict)
template.html
<script>
my_data = {{ my_dictionary|safe }};
</script>
because the data could be something like
{"</script><script>alert(123);</script>":""}
and forward slashes aren't escaped by default. Clearly the escaping by json.dumps may not 100% match the escaping in Javascript, which is where the problems come from.
Fixed solution
As far as I can tell, the following fixes the problem:
<script>
my_data = JSON.parse("{{ my_dictionary|escapejs }}");
</script>
If there are still issues, please post in the comments.