JavaScript customizations in the admin

Inline form events

You may want to execute some JavaScript when an inline form is added or removed in the admin change form. The formset:added and formset:removed events allow this. event.detail.formsetName is the formset the row belongs to. For the formset:added event, event.target is the newly added row.

In older versions, the event was a jQuery event with $row and formsetName parameters. It is now a JavaScript CustomEvent with parameters set in event.detail.

In your custom change_form.html template, extend the admin_change_form_document_ready block and add the event listener code:

{% extends 'admin/change_form.html' %}
{% load static %}

{% block admin_change_form_document_ready %}
{{ block.super }}
<script src="{% static 'app/formset_handlers.js' %}"></script>
{% endblock %}
app/static/app/formset_handlers.js
document.addEventListener('formset:added', (event) => {
    if (event.detail.formsetName == 'author_set') {
        // Do something
    }
});
document.addEventListener('formset:removed', (event) => {
    // Row removed
});

Two points to keep in mind:

  • The JavaScript code must go in a template block if you are inheriting admin/change_form.html or it won’t be rendered in the final HTML.

  • {{ block.super }} is added because Django’s admin_change_form_document_ready block contains JavaScript code to handle various operations in the change form and we need that to be rendered too.

Supporting versions of Django older than 4.1

If your event listener still has to support older versions of Django you have to use jQuery to register your event listener. jQuery handles JavaScript events but the reverse isn’t true.

You could check for the presence of event.detail.formsetName and fall back to the old listener signature as follows:

function handleFormsetAdded(row, formsetName) {
    // Do something
}

$(document).on('formset:added', (event, $row, formsetName) => {
    if (event.detail && event.detail.formsetName) {
        // Django >= 4.1
        handleFormsetAdded(event.target, event.detail.formsetName)
    } else {
        // Django < 4.1, use $row and formsetName
        handleFormsetAdded($row.get(0), formsetName)
    }
})
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