Sending data from a template to a JavaScript file via context variable

Question

Sending data from a template to a JavaScript file via context variable

This discussion thread here explored the use of variables in inline JavaScript within templates. Suppose I have individual .js files with scripts located in the static folder, like so:

utils.js

const createButton = (buttonCount) => {
    containerId = "myContainerId"
    container = document.getElementById(containerId)
    for (var i = 0; i < buttonCount; i++) {}
        newButton = document.createElement("button")
        newButton.value = "Test"
        newButton.id = "testButton" + i
        container.appendChild(newButton)
    }
}

createButton(buttonCount)

mytemplate.html

{% extends "base.html" %}
{% load static %}

{% block title %}Testpage{% endblock %}


{% block content-main %}
  <link href="{% static "css/mycss.css" %}" rel="stylesheet">
  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bulma/0.4.0/css/bulma.css" /> 

  <div id="myContainerId"></div>

  <script src="{% static 'js/utils.js' %}"> </script>

{% endblock %}

If a variable buttonCount is passed to this template through a view function's context, how can it be passed to the utils.js file to be utilized by the createButton() function?

views.py

def button_view(request):
    ...
    buttonCount = 5
    return render(request, 'mytemplate.html', {'buttonCount': buttonCount})

javascript django django-templates

Answer 1

Answer №1

Here are a few methods to achieve this:

Method 1: Using Input Field


    <input id="buttonCount" value = "{{buttonCount}}" style="display:none;">

You can then read the value of the element with id= buttonCount in utils.js.

Method 2: Inline Script **It's not recommended. Use Document.onload instead.
```
 <script>
 set_button_count({{buttonCount}});
 </script>
```

However, using inline script may cause issues if your utils.js is not loaded yet.

Method 3: Document.onload Place the script source in <head></head>


    <script src="{% static 'js/utils.js' %}" defer> </script>
    <script>
    document.addEventListener('onload',function(
    {set_button_count({{buttonCount}});
    })
    </script>

Ensure that set_button_count() is placed in utils.js
Using 'defer' will instruct the browser to only execute the script after the document has finished loading, preventing any issues related to script loading order.

Warning: Inline scripts should be used cautiously due to Content Security Policy (CSP) restrictions. To ensure security, inline scripts can be given a src attribute with a nonce value. CSP configurations can be implemented on Server Side through apache or Nginx servers, or within the HTML file if server-side control is limited.


<meta http-equiv="Content-Security-Policy" 
        content="default-src 'self';
        script-src 'self' 'nonce-{{nonce}}';">

The nonce value can be generated as follows:


    import random,base64
    
    def usersession_processor(request):
        user = request.user
        unbaked_nonce = '%32x' % random.getrandbits(16*8)
        unbaked_nonce = unbaked_nonce.encode('utf-8')
        baked_nonce = base64.b64encode(unbaked_nonce)
        baked_nonce = baked_nonce.decode('utf-8')

Then you can use

<script src="{{nonce}}"></script>

for secure inline scripts.

Answer 2

Here are a few methods to achieve this:

Method 1: Using Input Field


    <input id="buttonCount" value = "{{buttonCount}}" style="display:none;">

You can then read the value of the element with id= buttonCount in utils.js.

Method 2: Inline Script **It's not recommended. Use Document.onload instead.
```
 <script>
 set_button_count({{buttonCount}});
 </script>
```

However, using inline script may cause issues if your utils.js is not loaded yet.

Method 3: Document.onload Place the script source in <head></head>


    <script src="{% static 'js/utils.js' %}" defer> </script>
    <script>
    document.addEventListener('onload',function(
    {set_button_count({{buttonCount}});
    })
    </script>

Ensure that set_button_count() is placed in utils.js
Using 'defer' will instruct the browser to only execute the script after the document has finished loading, preventing any issues related to script loading order.

Warning: Inline scripts should be used cautiously due to Content Security Policy (CSP) restrictions. To ensure security, inline scripts can be given a src attribute with a nonce value. CSP configurations can be implemented on Server Side through apache or Nginx servers, or within the HTML file if server-side control is limited.


<meta http-equiv="Content-Security-Policy" 
        content="default-src 'self';
        script-src 'self' 'nonce-{{nonce}}';">

The nonce value can be generated as follows:


    import random,base64
    
    def usersession_processor(request):
        user = request.user
        unbaked_nonce = '%32x' % random.getrandbits(16*8)
        unbaked_nonce = unbaked_nonce.encode('utf-8')
        baked_nonce = base64.b64encode(unbaked_nonce)
        baked_nonce = baked_nonce.decode('utf-8')

Then you can use

<script src="{{nonce}}"></script>

for secure inline scripts.

Answer 3

Answer №2

It might not be the most recommended approach, but a possible way to achieve this is by utilizing Django template context. Place the script at the bottom of the page and include the button count as a variable in Django Templating Language. However, it's generally advised against mixing Django template variables with JavaScript.

To implement this, add a new block to your 'base.html' file within the body tag at the end like so:

{% block inline_javascript %}
{% enblock inline_javascript %}

Next, for the specific page where you want the function to execute, insert the script within the same tags at the bottom outside the 'block content'. Here's an example:

{% block inline_javascript %}
    <script>
        const createButton = ({{ buttonCount }}) => {
            containerId = "myContainerId";
            container = document.getElementById(containerId);
            for (var i = 0; i < {{ buttonCount }}; i++) {
                let newButton = document.createElement("button");
                newButton.value = "Test";
                newButton.id = "testButton" + i;
                container.appendChild(newButton);
            }
        };
    </script>
{% enblock inline_javascript %}

Answer 4

It might not be the most recommended approach, but a possible way to achieve this is by utilizing Django template context. Place the script at the bottom of the page and include the button count as a variable in Django Templating Language. However, it's generally advised against mixing Django template variables with JavaScript.

To implement this, add a new block to your 'base.html' file within the body tag at the end like so:

{% block inline_javascript %}
{% enblock inline_javascript %}

Next, for the specific page where you want the function to execute, insert the script within the same tags at the bottom outside the 'block content'. Here's an example:

{% block inline_javascript %}
    <script>
        const createButton = ({{ buttonCount }}) => {
            containerId = "myContainerId";
            container = document.getElementById(containerId);
            for (var i = 0; i < {{ buttonCount }}; i++) {
                let newButton = document.createElement("button");
                newButton.value = "Test";
                newButton.id = "testButton" + i;
                container.appendChild(newButton);
            }
        };
    </script>
{% enblock inline_javascript %}

Sending data from a template to a JavaScript file via context variable

Answer №1

Answer №2

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