# Django 2.0.14.dev20190701080343 documentation

# JavaScript

While most of Django core is Python, the `admin` and `gis` contrib apps contain JavaScript code.

Please follow these coding standards when writing JavaScript code for inclusion in Django.

## Code style

- Please conform to the indentation style dictated in the `.editorconfig` file. We recommend using a text editor with EditorConfig support to avoid indentation and whitespace issues. Most of the JavaScript files use 4 spaces for indentation, but there are some exceptions.
- When naming variables, use `camelCase` instead of `underscore_case`. Different JavaScript files sometimes use a different code style. Please try to conform to the code style of each file.
- Use the JSHint code linter to check your code for bugs and style errors. JSHint will be run when you run the JavaScript tests. We also recommended installing a JSHint plugin in your text editor.
- Where possible, write code that will work even if the page structure is later changed with JavaScript. For instance, when binding a click handler, use `$('body').on('click', selector, func)` instead of `$(selector).click(func)`. This makes it easier for projects to extend Django’s default behavior with JavaScript.

## JavaScript patches

Django’s admin system leverages the jQuery framework to increase the capabilities of the admin interface. In conjunction, there is an emphasis on admin JavaScript performance and minimizing overall admin media file size. Serving compressed or “minified” versions of JavaScript files is considered best practice in this regard.

To that end, patches for JavaScript files should include both the original code for future development (e.g. `foo.js`), and a compressed version for production use (e.g. `foo.min.js`). Any links to the file in the codebase should point to the compressed version.

### Compressing JavaScript

To simplify the process of providing optimized JavaScript code, Django includes a handy Python script which should be used to create a “minified” version. To run it:

    $ pip install closure
    $ python django/contrib/admin/bin/compress.py

Behind the scenes, `compress.py` is a front-end for Google’s Closure Compiler which is written in Java. The Closure Compiler library is not bundled with Django, but you can install it using pip as done above. The Closure Compiler library requires Java 7 or higher.

Please don’t forget to run `compress.py` and include the `diff` of the minified scripts when submitting patches for Django’s JavaScript.

## JavaScript tests

Django’s JavaScript tests can be run in a browser or from the command line. The tests are located in a top level `js_tests` directory.

### Writing tests

Django’s JavaScript tests use QUnit. Here is an example test module:

    QUnit.module('magicTricks', {
        beforeEach: function() {
            var $ = django.jQuery;
            $('#qunit-fixture').append('<button class="button"></button>');
        }
    });

    QUnit.test('removeOnClick removes button on click', function(assert) {
        var $ = django.jQuery;
        removeOnClick('.button');
        assert.equal($('.button').length, 1);
        $('.button').click();
        assert.equal($('.button').length, 0);
    });

    QUnit.test('copyOnClick adds button on click', function(assert) {
        var $ = django.jQuery;
        copyOnClick('.button');
        assert.equal($('.button').length, 1);
        $('.button').click();
        assert.equal($('.button').length, 2);
    });

Please consult the QUnit documentation for information on the types of assertions supported by QUnit.

### Running tests

The JavaScript tests may be run from a web browser or from the command line.

#### Testing from a web browser

To run the tests from a web browser, open up `js_tests/tests.html` in your browser.

To measure code coverage when running the tests, you need to view that file over HTTP. To view code coverage:

- Execute `python -m http.server` from the root directory (not from inside `js_tests`).
- Open http://localhost:8000/js_tests/tests.html in your web browser.

#### Testing from the command line

To run the tests from the command line, you need to have Node.js installed.

After installing Node.js, install the JavaScript test dependencies by running the following from the root of your Django checkout:

    $ npm install

Then run the tests with:

    $ npm test