django-js-asset 3.1.2

script tag with additional attributes for django.forms.Media

Note! Django 5.2 adds its own support for JavaScript objects. This library has a slightly different API and also supports much older versions of Django, and it also supports CSS and JSON tags.

Usage

Use this to insert a script tag via forms.Media containing additional attributes (such as id and data-* for CSP-compatible data injection.):

from js_asset import JS

forms.Media(js=[
    JS("asset.js", {
        "id": "asset-script",
        "data-answer": "42",
    }),
])

The rendered media tag (via {{ media.js }} or {{ media }} will now contain a script tag as follows, without line breaks:

<script type="text/javascript" src="/static/asset.js"
    data-answer="42" id="asset-script"></script>

The attributes are automatically escaped. The data attributes may now be accessed inside asset.js:

var answer = document.querySelector("#asset-script").dataset.answer;

Also, because the implementation of static differs between supported Django versions (older do not take the presence of django.contrib.staticfiles in INSTALLED_APPS into account), a js_asset.static function is provided which does the right thing automatically.

CSS and JSON support

Since 3.0 django-js-asset also ships a CSS and JSON media object which can be used to ship stylesheets, inline styles and JSON blobs to the frontend. It’s recommended to pass those through forms.Media(js=[]) as well since js is a simple list while css uses a dictionary keyed with the media to use for the stylesheet.

So, you can add everything at once:

from js_asset import CSS, JS, JSON

forms.Media(js=[
    JSON({"configuration": 42}, id="widget-configuration"),
    CSS("widget/style.css"),
    CSS("p{color:red;}", inline=True),
    JS("widget/script.js", {"type": "module"}),
])

This produces:

<script id="widget-configuration" type="application/json">{"configuration": 42}</script>
<link href="/static/widget/style.css" media="all" rel="stylesheet">
<style media="all">p{color:red;}</style>
<script src="/static/widget/script.js" type="module"></script>

Compatibility

At the time of writing this app is compatible with Django 4.2 and better (up to and including the Django main branch), but have a look at the tox configuration for definitive answers.

Extremely experimental importmap support

django-js-asset ships an extremely experimental implementation adding support for using importmaps.

One of the reasons why importmaps are useful when used with Django is that this easily allows us to use the file name mangling offered for example by Django ManifestStaticFilesStorage without having to rewrite import statements in scripts themselves.

Browser support for multiple importmaps is not generally available; at the time of writing (February 2025) it’s not even clear if Mozilla wants to support them ever, so merging importmaps is – for now – the only viable way to use them in production. Because of this the implementation uses a global importmap variable where new entries can be added to and a context processor to make the importmap available to templates.

The importmap object can be imported from js_asset. Usage is as follows:

# static is an alias for Django's static() function used in the
# {% static %} template tag.
from js_asset import JS, static, importmap

# Run this during project initialization, e.g. in App.ready or whereever.
importmap.update({
    "imports": {
        "my-library": static("my-library.js"),
    },
})

You have to add js_asset.context_processors.importmap to the list of context processors in your settings (or choose some other way of making the importmap object available in templates) and add {{ importmap }} somewhere in your base template, preferrably at the top before including any scripts.

When you’ve done that you can start profiting from the importmap by adding JavaScript modules:

# Example for adding a code.js JavaScript *module*
forms.Media(js=[
    JS("code.js", {"type": "module"}),
])

The code in code.js can now use a JavaScript import to import assets from the library, even though the library’s filename may contain hashes not known at programming time:

import { Stuff } from "my-library"