On Nov 16, 2013, at 3:32 AM, John Barton <[email protected]> wrote:
> Could someone help me understand why two goals for parsing JS is a good thing?
Hm, it sounds like you've assumed a conclusion already. Let me try to explain
anyway.
Scripts are for synchronous loading and evaluation; modules are for
asynchronous loading and evaluation. The former is not allowed to import, which
triggers I/O. The latter is allowed to import. There was always going to have
to be a syntactic split.
But there's more. I'll be explaining at this week's TC39 meeting some more
details about the intended model for browser integration. In short, declarative
code based on modules will use the <module> tag (or <script type="module">,
which will mean the same thing and allows polyfilling today). This is better
than <script async>, which was a hopeless idea. This also works beautifully for
fulfilling the promise of 1JS: a new, better initial environment in which to
run top-level application code without requiring versioning.
<module>
var x = 12; // local to this module, not exported on global
object
import $ from "jquery"; // asynchronous dependency, NBD
'$' in this // nope, because all globals are scoped to this
module
let y = 13; // yep, let works great because modules are strict
</module>
Same number of characters as <script>, better semantics, better global
environment, better language.
If you're not excited about ES6 yet, get excited. :)
Dave
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