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by tomphoolery 1087 days ago
From what I remember, reading the conversations over the years...the issue was twofold:

1. Because `require()` is "just a magic function", it can't be statically analyzed by a JS runtime prior to actually running the code. This leads to limitations with regards to tree-shaking and other optimizations.

2. The last point leads to the even bigger (and probably "deal-breaker") reason for the change, the desire to fetch packages from URL sources. Since the syntax cannot be parsed efficiently, runtimes like Deno and Bun would have a much harder time fetching resources from URLs prior to running the code. The idea here, IIRC, was to eliminate the install step, the need for centralization on a single package manager and registry, and a general "non-Web" approach to the idea of packages and modules in JS.

I believe the `import` syntax was chosen to allow transitions away from `require()`, so that your programs wouldn't just stop working if ESM was enabled.
2 comments
ComputerGuru 1087 days ago
Your first point is absolutely spot-on but I am curious as to how much treeshaking was on the minds of masses at the time. The tooling of that era didn't really have any good support for tree shaking even for non-AMD includes and it was quite experimental tech (as in, I don't think it was a decision making factor for the majority of the tools on the scene).

The second point actually isn't strictly valid. I've written my own "all-in-one" async custom loader [0] that can require() CommonJS/AMD includes, regular "add a script tag" includes w/out any exports, or even css stylesheets all asynchronously, with asynchronous dependency trees for each async dependency in turn. You can define in the HTML source code a "source map" that maps each dependency name to a specific URL, so that you don't need knowledge of the filesystem tree to load dependencies.

Ideally, this source map can be generated via the tooling you use to compile the code (e.g. `tsc` is aware of the path to each dependency) but I haven't written my own tool to generate the require path to url map.

[0]: https://github.com/mqudsi/loader

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skulk 1087 days ago
Why can't implementations tree-shake through require(x) where x can be determined statically and warn where x cannot?
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