Today I tried to help a friend who is a great computer scientist, but not a JS person use a JS module he found on Github. Since for the past 6 years my day job is doing usability research & teaching at MIT, I couldn’t help but cringe at the slog that this was. Lo and behold, a pile of unnecessary error conditions, cryptic errors, and lack of proper feedback. And I don’t feel I did a good job communicating the frustration he went through in the one hour or so until he gave up.
It went a bit like this…
Note: Names of packages and people have been changed to protect their identity. I’ve also omitted a few issues he faced that were too specific to the package at hand. Some of the errors are reconstructed from memory, so let me know if I got anything wrong!
John: Hey, I want to try out this algorithm I found on Github, it says to use
import functionName from packageName and then call
functionName(arguments). Seems simple enough! I don’t really need a UI, so I’m gonna use Node!
Lea: Sure, Node seems appropriate for this!
npm install packageName --save as recommended by the package’s README
Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension. SyntaxError: Cannot use import statement outside a module
John: But I don’t have a package.json…
npm init, it will generate it for you!
npm init, goes through the wizard, adds
type: "module" manually to the generated package.json.
SyntaxError: Cannot use import statement outside a module
Oddly, the error was thrown from an internal module of the project this time. WAT?!
Lea: Ok, screw this, just run it in a browser, it’s an ES6 module and it’s just a pure JS algorithm that doesn’t use any Node APIs, it should work.
John makes a simple index.html with a
<script type="module" src="index.js">
John loads index.html in a browser
Nothing in the console. Nada. Crickets.
Lea: Oh, you need to adjust your module path to import packageName. Node does special stuff to resolve based on
node_modules, now you’re in a browser you need to specify an explicit path yourself.
John looks, at his filesystem, but there was no node_modules directory.
Lea: Oh, you ran
npm install before you had a
package.json, that’s probably it! Try it again!
npm install packageName --save again
John: Oh yeah, there is a node_modules now!
John desperately looks in
node_modules to find the entry point
John edits his index.js accordingly, reloads index.html
Incorrect MIME type: text/html
Lea: Oh, you’re in
John: But why do I… ok fine, I’m going to start a localhost.
John starts localhost, visits his index.html under http://localhost:80
Incorrect MIME type: text/html
John: Sigh. Do I need to configure my localhost to serve JS files with a
Lea: What? No! It knows this. Um… look at the Networks tab, I suspect it can’t find your module, so it’s returning an HTML page for the 404, then it complains because the MIME type of the error page is not
Looks at node_modules again, corrects path. Turns out VS Code collapses folders with only 1 subfolder, which is why we hadn’t noticed.
FWIW I do think this is a good usability improvement on VS Code’s behalf, it improves efficiency, but they need to make it more visible that this is what has happened.
SyntaxError: missing ) after formal parameters
Lea: What? That’s coming from the package source, it’s not your fault. I don’t understand… can we look at this line?
John clicks at line throwing the error
John: I just wanted to run one line of code to test this algorithm…
John gives up. Concludes never to touch Node, npm, or ES6 modules with a barge pole.
Note that John is a computer scientist that knows a fair bit about the Web: He had Node & npm installed, he knew what MIME types are, he could start a localhost when needed. What hope do actual novices have?