[gjs/wip/ptomato/mozjs52: 37/38] docs: Overview of SpiderMonkey 52 features in NEWS

[Philip Chimento <pchimento src gnome org>]

commit 7753e1d2dbddb8acce7dad860ee023093affb482
Author: Philip Chimento <philip chimento gmail com>
Date:   Sun Jun 18 16:33:48 2017 -0700

    docs: Overview of SpiderMonkey 52 features in NEWS
    
    Distilled from Mozilla's documentation.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=784196

 NEWS |   57 +++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 files changed, 49 insertions(+), 8 deletions(-)
---
diff --git a/NEWS b/NEWS
index 306bd76..2d3f73e 100644
--- a/NEWS
+++ b/NEWS
@@ -1,33 +1,57 @@
 NEXT
 ----
 
-- New JavaScript features! This version of GJS is based on SpiderMonkey 45, an
+- New JavaScript features! This version of GJS is based on SpiderMonkey 52, an
   upgrade from the previous ESR (Extended Support Release) of SpiderMonkey 38.
-  Our plans are to continue upgrading to subsequent ESRs as maintainer
-  availability allows. Here are the highlights of the new JavaScript features.
+  GJS now uses the latest ESR in its engine and the plan is to upgrade again
+  when SpiderMonkey 59 is released in March 2018, pending maintainer
+  availability. Here are the highlights of the new JavaScript features.
   For more information, look them up on MDN or devdocs.io.
 
   * New language features
     + ES6 classes
+    + Async functions and await operator
     + Reflect - built-in object with methods for interceptable operations
 
   * New syntax
+    + Exponentiation operator: `**`
     + Variable-length Unicode code point escapes: `"\u{1f369}"`
     + Destructured default arguments: `function f([x, y]=[1, 2], {z: z}={z: 3})`
+    + Destructured rest parameters: `function f(...[a, b, c])`
     + `new.target` allows a constructor access to the original constructor that
       was invoked
+    + Unicode (u) flag for regular expressions, and corresponding RegExp.unicode
+      property
+    + Trailing comma in function parameter lists now allowed
 
   * New APIs
     + New Array, String, and TypedArray method: includes()
+    + TypedArray sort(), toLocaleString(), and toString() methods, to correspond
+      with regular arrays
+    + New Object.getOwnPropertyDescriptors() and Object.values() methods
+    + New Proxy traps: getPrototypeOf() and setPrototypeOf()
     + [Symbol.toPrimitive] property specifying how to convert an object to a
       primitive value
     + [Symbol.species] property allowing to override the default constructor
       for objects
-    + [Symbol.match] property allowing to customize matching behaviour in RegExp
-      subclasses
+    + [Symbol.match], [Symbol.replace], [Symbol.search], and [Symbol.split]
+      properties allowing to customize matching behaviour in RegExp subclasses
+    + [Symbol.hasInstance] property allowing to customize the behaviour of
+      the instanceof operator for objects
+    + [Symbol.toStringTag] property allowing to customize the message printed
+      by Object.toString() without overriding it
+    + [Symbol.isConcatSpreadable] property allowing to control the behaviour of
+      an array subclass in an argument list to Array.concat()
+    + [Symbol.unscopables] property allowing to control which object properties
+      are lifted into the scope of a with statement
+    + New Intl.getCanonicalLocales() method
     + Date.toString() and RegExp.toString() generic methods
+    + Typed arrays can now be constructed from any iterable object
+    + Array.toLocaleString() gained optional locales and options arguments, to
+      correspond with other toLocaleString() methods
 
   * New behaviour
+    + The "arguments" object is now iterable
     + Date.prototype, WeakMap.prototype, and WeakSet.prototype are now ordinary
       objects, not instances
     + Full ES6-compliant implementation of let keyword
@@ -39,17 +63,34 @@ NEXT
       followed by `new f` will not work)
     + It is now required to construct ArrayBuffer, TypedArray, Map, Set, and
       WeakMap with the new operator
+    + Block-level functions (e.g. `{ function foo() {} }`) are now allowed in
+      strict mode; they are scoped to their block
+    + The options.timeZone argument to Date.toLocaleDateString(),
+      Date.toLocaleString(), Date.toLocaleTimeString(), and the constructor of
+      Intl.DateTimeFormat now understands IANA time zone names (such as
+      "America/Vancouver")
 
   * Backwards-incompatible changes
     + Non-standard "let expressions" and "let blocks" (e.g.,
       `let (x = 5) { use(x) }`) are not supported any longer
+    + Non-standard flags argument to String.match(), String.replace(), and
+      String.search() (e.g. `str.replace('foo', 'bar', 'g')`) is now ignored
+    + Non-standard WeakSet.clear() method has been removed
     + Variables declared with let and const are now 'global lexical bindings',
       as per the ES6 standard, meaning that they will not be exported in
-      modules. If you cannot find symbols in your imported modules after the
-      upgrade, then likely you need to change "let" or "const" to "var" inside
-      your module file. For more information, read
+      modules. We are maintaining the old behaviour for the time being as a
+      compatibility workaround, but please change "let" or "const" to "var"
+      inside your module file. A warning will remind you of this. For more
+      information, read:
       https://blog.mozilla.org/addons/2015/10/14/breaking-changes-let-const-firefox-nightly-44/
 
+  * Experimental features (may change in future versions)
+    + String.padEnd(), String.padStart() methods (proposed in ES2017)
+    + Intl.DateTimeFormat.formatToParts() method (proposed in ES2017)
+    + Object.entries() method (proposed in ES2017)
+    + Atomics, SharedArrayBuffer, and WebAssembly are disabled by default, but
+      can be enabled if you compile mozjs yourself.
+
 Version 1.49.3
 --------------