[solved] Power BI custom visuals – $ is not a function when trying to load jquery plugins
When developing custom visuals for Microsoft's Power BI, a common issue developers encounter is the frustrating '$ is not a function' error message. This error typically arises when trying to integrate jQuery plugins within the Power BI sandbox environment. The sandbox, designed for security and resource isolation, manipulates the global window
object, leading to unexpected behavior with libraries that rely on global symbols, like jQuery.
Understanding the Problem
Before diving into the solution, it's crucial to grasp the root of the problem. Power BI custom visuals operate within a sandboxed iframe. This sandboxed environment provides a fake window
object to ensure security and prevent visuals from accessing or manipulating the host page and other visuals. While this sandboxing is beneficial for security, it complicates using external libraries that depend on global variables, such as jQuery.
In conventional web environments, jQuery registers itself on the global window
object as $
and jQuery
. However, in the Power BI sandbox, the altered window
object does not correctly expose jQuery, leading to the infamous '$ is not a function' error when scripts attempt to access jQuery through the $
shorthand.
The Solution
Fortunately, there's a clever workaround that helps navigate through this limitation. The essence of the solution lies in ensuring that jQuery is correctly recognized within the Power BI custom visual's sandboxed environment. Here's how you can do it:
- Ensure jQuery is Loaded: First, verify that jQuery is included in your custom visual project. It should be listed in the
externalJS
array within your pbiviz.json
file. This file serves as the project's configuration, and externalJS
specifies external JavaScript files to be included in your custom visual package. For jQuery, this typically looks like:
"node_modules/jquery/dist/jquery.js",
- Create a Bridge JavaScript File: The trick to making
$
recognized as a function is to create a bridge that explicitly assigns jQuery to $
within the context of your visual. Here's the scaffold of what the JavaScript file should contain:
var jQuery = typeof jQuery !== 'undefined'
? jQuery
: window['$'];
This snippet checks if jQuery
is already defined. If not, it tries to assign it from window['$']
, addressing the scenario where the sandboxed window
object misdirects the jQuery assignment.
- Update the
pbiviz.json
Configuration: The newly created JavaScript file needs to be properly positioned within the externalJS
array in your pbiviz.json
. Specifically, it should be included after jquery.js
but before any jQuery plugin you're using. For instance, if you're incorporating DataTables
as a jQuery plugin, your externalJS
array might look something like this:
[
"node_modules/jquery/dist/jquery.js",
"path/to/your/bridge/file.js",
"node_modules/datatables.net/js/jquery.dataTables.js"
]
This arrangement ensures that jQuery is loaded first, followed by the bridge that corrects the $
assignment, and finally, any plugins can safely utilize jQuery as expected.
Why This Solution Works
This workaround operates by preemptively addressing the issue of jQuery not being properly assigned to $
due to the sandbox's manipulation of the global window
object. By explicitly reassigning jQuery to $
in our bridge file and ensuring it's loaded before any plugins, we directly tackle the root cause of the '$ is not a function' error, allowing the rest of the scripts to execute seamlessly.
Conclusion
While working within the Power BI sandbox presents its challenges, especially when using global libraries like jQuery, understanding the environment and applying strategic solutions like the one discussed here can help overcome these obstacles. By carefully managing the order and manner in which external libraries are loaded, developers can build rich, interactive custom visuals that fully leverage the capabilities of jQuery and its ecosystem of plugins.
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