Call JavaScript function from Twig - javascript

I'm working on a Symfony2 project and I want to call a JavaScript function and pass an array of JSON objects (which I get from a controller) from a Twig.
But a first, very simple test already failed, like:
main.js:
function helloWorld(name) {
console.log("hello " + name);
}
linked to main.js in the twig and called the function:
<body>
<script>helloWorld("world!")</script>
{% block javascripts %}
<script src="{{ asset('js/main.js') }}"></script>
{% endblock %}
</body>
which results in a ReferenceError:
"Uncaught ReferenceError: helloWorld is not defined"
What do I have to do differently to make this work?
EDIT: Thanks to the two who took the time to answer. The described twig actually consists of a bunch of nested twigs and the placement of the javascript include was based on the Symfony documentation, guess that's why I didn't see the obvious. Should have detected the problem myself when phrasing the question though....

Invert the order of the functions:
<body>
{% block javascripts %}
<script src="{{ asset('js/main.js') }}"></script>
{% endblock %}
<script>helloWorld("world!")</script>
</body>

The script with the definition of the helloWorld definition is put after the function is executed. This means JavaScript doesn't yet know the function and triggers this error.
Solution: Put your javascript below your imports (before </body>, in the javascripts block for instance) or put the imports before the page javascript (in the head for instance).

Related

JavaScript only runs when both the code is inside the HTML and is called externally with <script src=...>

My JavaScript code only runs when the code is both inside the HTML file and called externally via
<script type="text/javascript" src="{{ url_for('static', filename='index.js') }}"></script>
<script>
var scroller = document.querySelector("#scroller");
...
</script>
I am using Flask and Jinja, with a file structure of:
/app
/static
index.js
/templates
base.html
myfile.html
routes.py
__init__.py
...
The code inside index.js is the exact same code between the <script> tags inside the HTML.
In terms of jinja and using block tags, base.html:
<body>
{% block content %}
<!-- typical HTML stuff here -->
{% endblock %}
<!-- some Bootstrap tags -->
<script ... ></script>
{% block script %}{% endblock %}
</body>
myfile.html:
<body>
...
{% block script %}
<script type="text/javascript" src="{{ url_for('static', filename='index.js') }}"></script>
{% endblock %}
<script>
...
</script>
The code itself works, and it worked not too long ago without this issue; I don't know what I changed to cause this, nor can I even imagine what could cause this. If there is more code that is required, I can easily share it.
Is there something I not understanding?
To note: I have had a similar issue trying to including external JavaScript code inside my HTML; at one point it wouldn't work, then it did, now it behaves the way I have described.
To further note: I have another .html file with its own external .js file that works fine.
Mr.#JakeJackson, Script in externl file never requires the same content to be available inside your inline code.
May be you are trying to process some elements and your script got executed before those elements are mounted to the document object.
A lazy solution to that problem is moving the external file linking tag to the bottom your HTML.Body.
OR
You can use defer attribute to your script element https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script
OR
If you have some libraries like jQuery included in your page, You can use the document.ready implementations in that
OR
you can implement your own document.ready like below
function myReady() {
return new Promise(function(resolve) {
function checkState() {
if (document.readyState !== 'loading') {
resolve();
}
}
document.addEventListener('readystatechange', checkState);
checkState();
});
};
myReady().then(function() {
// Put your app custom code here
});

How to defer JavaScript when using Django template variables?

I have a problem. I am doing all of this new fancy defer stuff when I load my JavaScript, as recommended by lighthouse while working on PWA.
{% block head_content %}
<script defer src={% static 'js/jquery.min.js' %}></script>
{% endblock %}
If I was just doing this in a Django tempalte, it would not be a problem, I could just move the <script> content to a .js file and defer that also:
{% block content %}
<script>
$( jquery thing
let x = 0; // Do jQuery stuff with NO json_data
);
</script>
{% endblock %}
However, I have a Django application that is doing something like:
{% block content %}
<script>
$( jquery thing
{{ json_data|safe }} // Do jQuery stuff with json_data
);
</script>
{% endblock %}
So if I try and move the script to a separate .js file I get: SyntaxError: expected property name, got {.
This very popular Q&A seems not to work if you get $ is not defined due to using defer, as noted by the top comment. Is my only option to put the script above the portion of the code that uses jquery in the body with no defer? If so, this limits the usefulness of Django's template inheritance.
{% block content %}
<script>
<script src={% static 'js/jquery.min.js' %}></script> // Add above each first-use of jQuery (along with every other relevant library)
$( jquery thing
{{ json_data|safe }} // Do jQuery stuff with json_data
);
</script>
{% endblock %}
I haven't been using Django in a while now, but I don't think you can "defer" that script tag inside your template. That said, you could try one of the following:
01: Load your json_data into a variable that you can access from an external .js file.
Something like:
var myJsonData = "{{ json_data|safe }}";.
Check this thread here for more info.
02: Another option is to create an endpoint that will return that json_data and call it from an external .js using ajax. Then you can use the data to do whatever you need.
Something like
$.ajax({
url: "my_django_endpoint",
success: function(result){
// Do jQuery stuff;
}
});
Check this thread here for more info.
We used a framework called T3JS that has a neat way of implementing Option 01 using context. (if you wanna take a look under the topic getConfig).
Hope it helps :)

jQuery not recognized in extended html python flask

Not sure what is going on here. It seems that jQuery is not "extended" from a base.html file to an external one.
I have:
#base.html
<!doctype html>
<html class="no-js" lang="en">
<head>
...
... # css imports
</head>
<body>
# some fixed stuff
{% block body %}
# some stuff specific to base.html
{% endblock %}
# js imports at the end of the body
<script src="static/js/jquery-3.1.0.min.js"></script>
... # various other js
</body>
</html>
Then I have another html file:
#test.html
{% extends "base.html" %}
{% block body %}
# some stuff
<script type="text/javascript">
$(document).ready( function () {
alert("foo")
} );
</script>
{% endblock %}
Now, I don't get any alert. However, if I use plain javascript it works as expected.
I noticed that if I import again jQuery in test.html, jQuery works fine. But what's the point of extending then?
There must be something that I'm missing. By the way, this seems to happen only with jQuery, all other javascript libraries seem to be extended fine.
It's really very simple. When the following code runs, it needs to run using jQuery.
<script type="text/javascript">
$(document).ready( function () {
alert("foo")
} );
</script>
However, your jQuery is being loaded AFTER these commands, whereas, it needs to be placed BEFORE that.
It's like you're drinking water from a glass before you're putting water in it. You need to put the water in the glass first and then drink it. I don't know if this example makes it easy or not.
Add this line.I hope this will work.
<script type="text/javascript" src="{{ url_for('static', filename='js/jquery-3.1.0.min.js')
}}"></script>
At the moment $(document).ready( function () { executes, $ hasn't been aliased to jQuery, which has yet to load.

JMSTwigJsBundle doesn't compile

In a search to optimize the possibility of my application made with symfony2, I choose the JMSTwigJsBundle to allow the usage of twig template both frontend or backend.
I use composer to install bundles and symfony (it is the 2.7.3 version)
I began to follow a tutorial who bring me to add both FOSJsRoutingBundle and JMSTwigJsBundle. The first one, installed first, work perfectly, but the second brought me different kinds of problem, beginning with "Uncaught ReferenceError: goog is not defined". I resolved it by adding the following content :
these two lines on app/autoloader.php as described in the official documentation ( http://jmsyst.com/bundles/JMSTwigJsBundle ):
$loader->add('JMS', __DIR__.'/../vendor/jms/twig-js-bundle');
$loader->add('TwigJs', __DIR__.'/../vendor/jms/twig-js/src');
The app/AppKernel.php is set with the following line :
new JMS\TwigJsBundle\JMSTwigJsBundle(),
I also add to my app/config.yml these lines :
Filters:
twig_js:
resource: "%kernel.root_dir%/../vendor/jms/twig-js-bundle/JMS/TwigJsbundle/Resources/config/services.xml"
apply_to: "\.twig$"
So, we can found inside my layout.html.twig the following lines
{% javascripts
'js/fos_js_routes.js'
'%kernel.root_dir%/../vendor/jms/twig-js/twig.js
'#NameSpaceNameBundle/Resources/views/customFolder/example.html.twig'%}
<script language="javascript" src="{{ asset_url }}"></script>
{% endjavascripts %}
And, thank to the filters on the config file, we don't need to add the filter line.
These modifications are from : https://github.com/schmittjoh/JMSTwigJsBundle/pull/13 post 3
I also do modifications presentend here : https://github.com/schmittjoh/twig.js/issues/35 post 2 :
I found a way to fix this issue by copyng the file
/Symfony/vendor/bundles/JMS/TwigJsBundle/Resources/config/services.xml
to
/Symfony/vendor/bundles/Symfony/Bundle/AsseticBundle/Resources/config/filters/twig_js.xml
and changing the service id from twig_js.assetic_filter to
assetic.filter.twig_js.
Every of theses modifications bring me to a new error :
Uncaught SyntaxError: Unexpected token %
on the created file "exemple.html.twig.js:1". For information, the twig file looks like :
{% twig_js name="example" %}
the html code
And the content generated on the new file is... exactly the same content than the twig's file.
So, please, what did I have to do to make it work ? Thank's
To make it work to and have a compiled version of any .twig, I had to include the "YUIcompressor" to the app/config/config.yml :
yui_css:
jar: "%kernel.root_dir%/Resources/java/yuicompressor.jar"
yui_js
jar: "%kernel.root_dir%/Resources/java/yuicompressor.jar"
and add the appropriate file to the associate path.
Then I add to the layout.html.twig
{% javascripts filter='?yui_js'
'js/fos_js_routes.js'
'%kernel.root_dir%/../vendor/jms/twig-js/twig.js
'#NameSpaceNameBundle/Resources/views/customFolder/example.html.twig'%}
<script language="javascript" src="{{ asset_url }}"></script>
{% endjavascripts %}
Finally I use the app/console assets:install and app/console assetic:dump to check if they're is nothing wrong, refreshed and it was ok (at least for me).

Django/jQuery: handling template inheritence and JS files loading

In Django, how can you handle the fact that you need to wait for that a JS file is loaded before actually using it?
let's see the problem with this example:
base.html
<!DOCTYPE html>
<html>
<head>...</head>
<body>
{% include "content.html" %}
<script src="jquery.js"></script>
<script src="awesome-script.js"></script>
</body>
</html>
content.html
<script>
$(document).ready(function(){
...
});
</script>
This logically fail ($ is undefined). I could load jQuery before calling the script, but I'm trying to avoid loading JS file before my main content to keep the website loading as fast as possible.
So, what can I do? Thanks.
Extending Wtower's suggestion - keep his accepted.
I would really insist on using the template inheritance based approach in his examples. I would like to introduce a few more elements to that approach, to cover some other common needs :
<!DOCTYPE html>
<html>
<head>{% block scripts-head %}{% endblock %}</head>
<body>
{% block content %}{% endblock %}
{% block scripts %}
<script src="jquery.js"></script>
{% endblock %}
<script>{% block script-inline %}{% endblock %}</script>
</body>
</html>
There are 3 ideas here:
Adding a placeholder in the header, in case you could need scripts there at some point. Self explanatory.
Including common scripts in the base file. If they are common, the belong in the base file, you should not have to repeat yourself in every template. Yet you put it inside the block, so it can be overriden along the hierarchy.
{% extends "base.html" %}
{% block scripts %}
{{ block.super }}
<script src="a-local-lib.js"></script>
{% endblock %}
The key is in using {{ block.super }} to bring any script that was defined in the parent template. It works especially well when you have several levels of inheritance in your templates. You get to control whether script go before or after inherited scripts. And of course, you can completely override the block, not including {{ block.super }} if you so wish.
Basically the same idea, but with raw javascript. You use it the same way: every template that needs to include some inline javascript will have its {{ block script-inline }}, and will start with {{ block.super }} so whatever the parent put in there is still included.
For instance, I use Ember in my project, and have a couple of initializers to setup project settings and load bootstrap data. My base app-loading templates has a global project settings initializer, and child templates define local settings and data.
Since your script uses jQuery, you can simply use the $(document).ready() and $(window).load() functions of jQuery to bind a function on the event that DOM is ready and all window contents have been loaded, respectively.
If you do not use jQuery, take a look at these relative questions to understand how to imitate the above behaviour with pure JS:
pure JavaScript equivalent to jQuery's $.ready() how to call a function when the page/dom is ready for it
Javascript - How to detect if document has loaded
EDIT 1: The inclusion order matters. You have to include the jQuery scripts before any scripts that require jQuery are executed.
EDIT 2: You can organize your templates better by keeping the scripts separately from the main content, either with a second template:
base.html
<!DOCTYPE html>
<html>
<head>...</head>
<body>
{% include "content.html" %}
{% include "js.html" %}
</body>
</html>
js.html
<script src="jquery.js"></script>
<script src="awesome-script.js"></script>
<script>
$(document).ready(function(){
...
});
</script>
(in this case you render base.html)
Or with blocks (recommended):
base.html
<!DOCTYPE html>
<html>
<head>...</head>
<body>
{% block content %}{% endblock %}
{% block scripts %}{% endblock %}
</body>
</html>
content.html
{% extends 'base.html' %}
{% block content %}
...
{% endblock %}
{% block scripts %}
<script src="jquery.js"></script>
<script src="awesome-script.js"></script>
<script>
$(document).ready(function(){
...
});
</script>
{% endblock %}
(in this case you render content.html)

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