wintercg-proposal importScripts / importScript

history

this was a tc39 proposal but tc39 will not integrate something that breaks the web so we would need to make this a single url taking function called importScript this algins also with our goals as ECMAScript has no concept of i/o its better to agree on that on the implementer level:

nodejs, justjs, deno, chromium,

Explainer

The importScripts() method of the GlobalScope interface synchronously imports one or more scripts into the scope. (inlining) current implementations: https://html.spec.whatwg.org/multipage/workers.html#dom-workerglobalscope-importscripts-dev

importScripts(...urls) Fetches each URL in urls, executes them one-by-one in the order they are passed, and then returns (or throws if something went amiss).

• designed to work in Scripts and Modules
• designed to work without additional resolve hooks

there is a voting on going to rename this to importScript() and let it only handle a single url to not colide with existing environemnt checks for webworkers

Importent please give comments or up down votes for

• issue: #2 Web Compat problem environment detection

Status

Champion(s): champion name(s) Author(s): non-champion author(s), if applicable Stage: -1

Implemented: importScript

• es4x
• justjs (v8 embedder framework) linux only at present Implemented: importScripts
• Web Worker API Implementing: importScripts
• es4x
• justjs (v8 embedder framework) linux only at present Integration Phase
• NodeJS (build nodejs releases with import script from 18+ via snapshot feature)
• NodeJS (offer npm package with subpackages cjs mjs)
• Deno (needs talk to deno land as i am not sure how they bundle at present but bundler integration will be the key)
• GraalJS is at present related to es4x as that is the only runtime implementation with graal-node Implemented: importScript and importScripts

Motivation

Why is this important to have in the JavaScript language? sync imports are needed:

• in both front-end and back-end programming.
• They are the only way to handle sideEffects of native code without loosing events.
• ESM is only async so it misses events from the before the first process.nextTick
• There is no universal sync Module system for ECMAScript Engines while it is needed in some Engines
• require in nodejs for example is bad because it mixes CJS Modules, importScripts, nativRequire (.node modules and c++ bindings)
• browser can only import a bunch of scripts via adding multiple script tags in the render engine there is no equal function in the JS Runtime.
• it would make experiments a lot of easyer without diskwrites as it would no longer be needed to join/merge files for tests
• is like programatical inlining offers a lot of magic.
• offers a consistent way for ECMAScript Engines to load and run scripts without using eval directly. while it is equal to eval or in NodeJS VM.runInThisContext
• is part of a bigger effort to algin ECMAScript engines and reduce code rewrites.
• good for backward compatability
• introduces a none module based ECMAScript Environment as standard starting point which is needed in all ECMAScript Runtime Implementations
• makes user land environment modifications / mocking easyer as they happen sync in the first process.Tick
• Allows code reuse between diffrent module systems.

Importent Knowleg

ECMAScripts do exist in 2 main Flavors: Scripts and Modules everything that has export {} or import is a module everything else is a Script in Some ECMAScript Engines like NodeJS are more Module Systems Implemented for example .node modules or .cjs out of ECMAScript view this implementations are Scripts.

The ECMAScript Module System ESM is Async by Design but this is about a Sync import Process.

Use cases

Some realistic scenarios using the feature, with both code and description of the problem; more than one can be helpful.

Server-side sync import: Say you want to import a ECMAScript Script. Then, you would normally have to create a file and inline the code from the other file. If it's in the standard, it'd be easier as you can simply create a single file that is referencing the files that contain the codes and executes them in order.

var urls = ['url1','url2']
importScripts(...urls);

Browser-side sync import: browsers do only support sync script imports via Githubissues.