Revision: 5433
Author: [email protected]
Date: Sat Jun 1 12:34:00 2013
Log: Edited wiki page SES through web user interface.
http://code.google.com/p/google-caja/source/detail?r=5433
Modified:
/wiki/SES.wiki
=======================================
--- /wiki/SES.wiki Thu Feb 21 08:40:59 2013
+++ /wiki/SES.wiki Sat Jun 1 12:34:00 2013
@@ -6,13 +6,13 @@
= Introduction =
-SES is mostly defined as a fail-stop subset of ES5 that should compatibly
run all ES5 code that follows recognized ES5 best practices. The SES
restrictions support the writing of defensively consistent abstractions --
object abstractions that can defend their integrity while being exposed to
untrusted but confined objects.
+SES is mostly defined as a fail-stop subset of ES5. SES should compatibly
run all ES5 code that follows recognized ES5 best practices. The SES
restrictions support the writing of defensively consistent abstractions --
object abstractions that can defend their integrity while being exposed to
untrusted but confined objects.
This page is for hard core developers, to document precisely the
differences between the various forms of SES, and how these differ from
ES5. Introductory and tutorial material will appear elsewhere. _*where?*_
= ES6 extras: `WeakMaps` =
-There is one crucial way in which SES is more than a subset of ES5 though
still a subset of ES6 -- the inclusion of the
[http://wiki.ecmascript.org/doku.php?id=harmony:weak_maps WeakMap
abstraction] proposed for !EcmaScript 6. Over time, as more of ES6 settles
down and becomes available in !JavaScript implementations, we expect to
make more of these features available within SES as well. Note that
`WeakMap` is always available in SES, whether or not it is available yet on
the underlying !JavaScript platform. (When it does not derive from platform
provided `WeakMap`s, the
[http://code.google.com/p/google-caja/source/browse/trunk/src/com/google/caja/ses/WeakMap.js
emulated WeakMaps] are necessarily leaky, but this is technically a quality
of implementation issue rather than a correctness issue.)
+There is one crucial way in which SES is more than a subset of ES5 though
still a subset of ES6 -- the inclusion of the
[http://wiki.ecmascript.org/doku.php?id=harmony:weak_maps WeakMap
abstraction] proposed for !EcmaScript 6. Over time, as more of ES6 settles
down and becomes available in !JavaScript implementations, we expect to
make more of these features available within SES as well. Note that
`WeakMap` is always available in SES, whether or not it is available yet on
the underlying !JavaScript platform. (When it does not derive from platform
provided `WeakMap`s, the
[http://code.google.com/p/google-caja/source/browse/trunk/src/com/google/caja/ses/WeakMap.js
emulated WeakMaps] are necessarily leaky, but this is technically a
quality-of-implementation issue rather than a correctness issue.)
= Idealized SES vs ES5 vs ES5 best practices =
@@ -208,7 +208,7 @@
== `this`-binding of Global Function Calls ==
-In ES3, ES5-non-strict, when a global function is called as a function,
its `this`-binding is the global object. In ES5-strict and in Source-SES,
its `this`-binding is `undefined`. Unfortunately, the Target-SES behavior
is more like the ES3 and ES5-non-strict behavior, but the global in
question is the imports object (or virtual global) for that Target-SES
evaluation.
+In ES3, ES5-non-strict, when a global function is called as a function,
its `this`-binding is the global object. In ES5-strict and in Source-SES,
its `this`-binding is `undefined`. Unfortunately, the Target-SES behavior
is more like the ES3 and ES5-non-strict behavior, but the global in
question is the scope object for that Target-SES evaluation.
The above transformation which turns global functions into function
expressions also addresses this difference in semantics.
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