Domenic Denicola wrote:
From: Brendan Eich [bren...@mozilla.com]
You still value the
```js
(x == y&& typeof x == y)<=> x === y
```
invariant, right? That's the motivation for decimal, int64, etc. having their constructor-named
"decimal", "int64", etc., typeof-result strings.
You have brought up this invariant in many threads.
Yes, and I've written about why invariants matter on occasion -- perhaps
you missed that :-P.
https://mail.mozilla.org/pipermail/es-discuss/2008-September/007610.html
"""
Postel's Law means you accept everything that flies in ES1, and have
trouble being less liberal in ES2+. Web authors crawl the feature
vector space and find all the edges, so at least what you did not
accept in v1 becomes law. But these are generalizations from
experience with invariants such as typeof x == "object"&& !x => x
=== null and typeof x == typeof y => (x == y<=> x === y).
Beyond this conservatism in breaking invariants based on experience,
it turns out that % and / results do flow into array indexes. From
SunSpider's 3d-raytrace.js....
"""
Could you explain its importance and value? My feeling is that nobody uses
`==`,
Your feeling is wrong. == is used (I miss Google codesearch) widely on
the web.
so a relation tying together `==`, `typeof`, and `===` doesn't really impact
anything people use.
See above. Language designers value and conserve invariants based on
long experience with painful counterexamples.
Put another way: why do you feel this is an important base invariant of the
language, to be preserved, rather than just an equality that happens to fall
out of what we have in the language now?
It's not an equality, rather a two-way implication. It helps us reason
about all three of typeof, ==, and === as we evolve JS. It's not noise,
and not nothing. We could deliberately break it, but for what win?
/be
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