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NPM javascript throws error "Uncaught ReferenceError: module is not defined"

Asked by Danijel
25 days ago.


We have an ASP.NET Core app (without angular, react or vue).
We are pulling the file***/2023.1.5488.tar.gz to be used in our local npm repo.

in our package.json we have the following (other dependencies were removed for this post):
  "version": "1.0.0",
  "name": "",
  "private": true,
  "dependencies": {
    "daypilot-pro-javascript": "^2023.1.5488"

in our bundleconfig.json we have this configuration:

    "outputFileName": "wwwroot/js/bundle-daypilot.js",
    "inputFiles": [

in our Index.xshtml view we are using this line to load the JavaScript:

<script src="~/js/bundle-daypilot.js" asp-append-version="true"></script>

but on loading the page we get a javascript error:

bundle-daypilot.js?v=GvIg2_avHtwOVk9WM8w3DdafmP7bc-buTMWg2sVbWq0:37 Uncaught ReferenceError: module is not defined
    at bundle-daypilot.js?v=GvIg2_avHtwOVk9WM8w3DdafmP7bc-buTMWg2sVbWq0:37:13
    at bundle-daypilot.js?v=GvIg2_avHtwOVk9WM8w3DdafmP7bc-buTMWg2sVbWq0:37:48

If we compare the file that we manually download and the one that we get by npm link,
the script from npm has this line extra:


Question: How do we use the npm package in our project if we pull the javascript from npm?

Comment posted by Danijel
25 days ago.

replacing the content from daypilot-all.min.js works, but still we need to know how to use it over npm.

Answer posted by Dan Letecky [DayPilot]
25 days ago.

The JavaScript NPM package (daypilot-pro-javascript) defines a CommonJS module which can't be used directly in the browser. The purpose is to allow using DayPilot in a Node project.

In the browser, you can load a CommonJS module using require.js (

You can also create your own package from daypilot-all.min.js from the zip download.

Comment posted by Danijel
24 days ago.

A check for whether module is undefined would allow us to run your code in a Node context, but also with pure browser-side JS.

Something like this:

if (typeof module === 'object') {
    module.exports = ...;

Is there an example how to load this with RequireJS?

Comment posted by Dan Letecky [DayPilot]
24 days ago.

In the latest sandbox build (2023.1.5506), the module registration is now conditional:

You can also work around this issue (with the current version) by declaring a "module" object in the global context:

var module = {};

That would be easier than using RequireJS.

Comment posted by Danijel
24 days ago.

Thank you, we will wait for the 2023.1.5506 release as it requires no further changes to our current app.

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