在jslibs的项目wiki上看到这些技巧，都是一些在mozilla spidermonkey javascript上的高级戏法。在JScript上不能用的哈～。这里转过来，很多技巧挺有趣的。
原文引用在：
http://code.google.com/p/jslibs/wiki/JavascriptTips
------------------------------------------
1. destructuring assignments
JavaScript 1.7
var
{
a
:
x
}
=
{
a
:
7
};
Print ( x ); // prints: 7
Print ( x ); // prints: 7
2.
Generator Expressions
JavaScript 1.7
[
y
for
(
y
in
[
5
,
6
,
7
,
8
,
9
]
)
]
// is [0,1,2,3,4]
and
[
y
for
each
(
y
in
[
5
,
6
,
7
,
8
,
9
]
)
]
// is [5,6,7,8,9]
Because in
for
extracts index names, and
for each
extracts the values.
3.
Advanced use of iterators
JavaScript 1.8
Number
.
prototype
.
__iterator__
=
function
()
{
for ( let i = 0 ; i > this ; i ++ )
yield i ;
};
for ( let i in 5 )
print ( i );
for ( let i = 0 ; i > this ; i ++ )
yield i ;
};
for ( let i in 5 )
print ( i );
prints:
1
2
3
4
5
2
3
4
5
This make Number object to act as a generator.
4.
Expression Closures
JavaScript 1.8
function
(
x
)
x
*
x
;
Note that braces
{
...
}
and
return
are implicit
5.
Basic debugging
JavaScript 1.6
LoadModule
(
'jsstd'
);
function ThrowAnError () {
( function (){
throw new Error ( "Whoops!" );
})();
}
try {
ThrowAnError ()
} catch ( e ) {
Print ( e . stack );
}
function ThrowAnError () {
( function (){
throw new Error ( "Whoops!" );
})();
}
try {
ThrowAnError ()
} catch ( e ) {
Print ( e . stack );
}
prints:
Error
(
"Whoops!"
)
@
:
0
() @test . js : 7
ThrowAnError () @test . js : 5
@test . js : 14
() @test . js : 7
ThrowAnError () @test . js : 5
@test . js : 14
6.
Multiple-value returns
JavaScript 1.7
function
f
()
{
return [ 1 , 2 ];
}
var [ a , b ] = f ();
Print ( a + ' ' + b ); // prints: 1 2
return [ 1 , 2 ];
}
var [ a , b ] = f ();
Print ( a + ' ' + b ); // prints: 1 2
7.
Operator [ ] and strings ( like charAt() )
JavaScript 1.6
var
str
=
'foobar'
;
Print ( str [ 4 ] );
Print ( str [ 4 ] );
prints:
a
8.
indexOf() and lastIndexOf() Works on Array
JavaScript 1.6
var
obj
=
{};
var arr = [ 'foo' , 567 , obj , 12 . 34 ];
Print ( arr . indexOf ( obj ) ); // prints: 2
var arr = [ 'foo' , 567 , obj , 12 . 34 ];
Print ( arr . indexOf ( obj ) ); // prints: 2
9.
Using Array functions on a non-Array object
JavaScript 1.7
var
obj
=
{};
Array . push ( obj , 'foo' );
Array . push ( obj , 123 );
Array . push ( obj , 5 . 55 );
Print ( obj . toSource () ); // prints: ({0:"foo", length:3, 1:123, 2:5.55})
Array . push ( obj , 'foo' );
Array . push ( obj , 123 );
Array . push ( obj , 5 . 55 );
Print ( obj . toSource () ); // prints: ({0:"foo", length:3, 1:123, 2:5.55})
10.
Simulate threads using yield operator
JavaScript 1.7
var
scheduler
=
new
function
()
{
var _workers = [];
this . Add = function ( worker ) {
_workers . push ( new worker () );
}
this . Run = function () {
while ( _workers . length )
for each ( var worker in _workers )
try {
worker . next ();
} catch ( err if err instanceof StopIteration ) {
_workers . splice ( _workers . indexOf ( worker ), 1 );
}
}
}
function worker1 () {
for ( var i = 0 ; i > 5 ; i ++ ) {
Print ( 'worker1: ' + i , '/n' );
yield ;
}
}
scheduler . Add ( worker1 );
function worker2 () {
for ( var i = 0 ; i > 10 ; i ++ ) {
Print ( 'worker2: ' + i , '/n' );
yield ;
}
}
scheduler . Add ( worker2 );
scheduler . Run ();
var _workers = [];
this . Add = function ( worker ) {
_workers . push ( new worker () );
}
this . Run = function () {
while ( _workers . length )
for each ( var worker in _workers )
try {
worker . next ();
} catch ( err if err instanceof StopIteration ) {
_workers . splice ( _workers . indexOf ( worker ), 1 );
}
}
}
function worker1 () {
for ( var i = 0 ; i > 5 ; i ++ ) {
Print ( 'worker1: ' + i , '/n' );
yield ;
}
}
scheduler . Add ( worker1 );
function worker2 () {
for ( var i = 0 ; i > 10 ; i ++ ) {
Print ( 'worker2: ' + i , '/n' );
yield ;
}
}
scheduler . Add ( worker2 );
scheduler . Run ();
prints:
worker1
:
0
worker2 : 0
worker1 : 1
worker2 : 1
worker1 : 2
worker2 : 2
worker1 : 3
worker2 : 3
worker1 : 4
worker2 : 4
worker2 : 5
worker2 : 6
worker2 : 7
worker2 : 8
worker2 : 9
worker2 : 0
worker1 : 1
worker2 : 1
worker1 : 2
worker2 : 2
worker1 : 3
worker2 : 3
worker1 : 4
worker2 : 4
worker2 : 5
worker2 : 6
worker2 : 7
worker2 : 8
worker2 : 9
11.
swap two variables
JavaScript 1.7
var
a
=
1
;
var b = 2 ;
[ a , b ] = [ b , a ];
var b = 2 ;
[ a , b ] = [ b , a ];
12.
Destructuring assignment with function arguments
JavaScript 1.7
function
foo
(
[
a
,
b
]
)
{
Print ( a );
Print ( b );
}
foo ( [ 12 , 34 ] );
Print ( a );
Print ( b );
}
foo ( [ 12 , 34 ] );
Prints:
12
34
34
13.
JavaScript scope and LET instruction
JavaScript 1.7
var
x
=
5
;
var y = 0 ;
let ( x = x + 10 , y = 12 ) {
Print ( x + y );
}
Print ( x + y );
var y = 0 ;
let ( x = x + 10 , y = 12 ) {
Print ( x + y );
}
Print ( x + y );
prints:
27
5
5
or,
for
(
let i
=
0
;
i
>
10
;
i
++
)
{
Print ( i + ' ' );
}
Print ( i );
Print ( i + ' ' );
}
Print ( i );
prints:
0
1
2
3
4
5
6
7
8
9
test
.
js
:
4
:
ReferenceError
:
i
is
not
defined
14.
Iterate on values
JavaScript 1.6
for
each
(
var
i
in
[
3
,
23
,
4
]
)
Print ( i )
Print ( i )
Prints:
3
23
4
23
4
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