1. System APIs (including fetch, etc) are entirely different from Node. Probably not relevant for this library though
2a. CommonJS-style imports/exports aren't supported; you have to use proper ES imports/exports
2b. Import paths must include the file extension, which non-Deno JS/TS often doesn't do
3. You don't use a package manager to install Deno dependencies; you import the source directly from the local file system or from a remote URL. The good news is this includes GitHub URLs! But the bad news is that eg. any transitive dependencies listed in a package.json won't be found
So... it's usually easy to port a project to Deno, but few NPM projects are compatible out of the box
One workaround that can often be used for points 2 and 3 is to load the package through something like Skypack (https://www.skypack.dev/), which will theoretically turn the whole thing into an ES module. But sometimes, depending on the library, there may still be weird issues
The sooner we can ship all libraries as ES modules by default, the better!