A package will not install or work

No connection

Searching npm needs a connection. With none, the search box in the Packages window shows a warning mark, and the list says You’re offline. Hover the mark: You're offline — search and install need a connection. What's already installed still works.

Connect to the internet, and search again. Packages that are already installed keep working offline.

Install errors JSpark+

Installing, updating and removing packages is JSpark+. In JSpark, the packages that Starters use and imports from a CDN work without it. An install that cannot reach npm says one of these:

• Can’t reach npm. Check your connection.
• npm stopped responding. Check your connection.
• Not cached. Go online to install.

Connect, and press Install again.

A skipped setup step

Some npm packages run a setup script when they are installed, for example to download a program they need. JSpark never runs these scripts. When a package, or a package it uses, has one, the package’s page in the Packages window says so:

The package may still work. If it does not, the error comes when you use it. A package that downloads a binary for Node, for example, fails at require or import. There is no way to run the step in JSpark. Try a package that does the same work in plain JavaScript.

A Web package offline

A package is installed once, for Node and for web pages. The web version is built from esm.sh, so it needs a connection the first time. Installed offline, the package works in Node at once, and its page in the Packages window says:

Until then, a web page that imports it gets an error in its console: the package isn't ready for Web Snippets yet — its Web version needs a connection to finish installing. Connect to the internet. The web version finishes by itself. Then run the page again. From then on, it works offline.

See Packages.