Previously:
Without `--screw-ie`, UglifyJS would always leak names of function
expressions into the containing scope, as if they were function
declarations. That was to emulate IE<9 behavior. Code relying on this
IE bug would continue to work properly after mangling, although it would
only work in IE (since other engines don't share the bug). Sometimes
this broke legitimage code (see #153 and #155).
With `--screw-ie` the names would not be leaked into the current scope,
working properly in legit cases; but still it broke legit code when
running in IE<9 (see #24).
Currently:
Regardless of the `--screw-ie` setting, the names will not be leaked.
Code relying on the IE bug will not work properly after mangling.
<evil laughter here>
Without `--screw-ie`: a hack has been added to the mangler to avoid
using the same name for a function expression and some other variable in
the same scope. This keeps legit code working, at the (negligible,
indeed) cost of one more identifier.
With `--screw-ie` you allow the mangler to name function expressions
with the same identifier as another variable in scope. After mangling
code might break in IE<9.
Oh man, the commit message is longer than the patch.
Fix#153, #155
The problem with reading synchronously from /dev/stdin is that you can get a
spurious EOF when the input buffer is empty, even if more content is coming. Now
STDIN is read from a loop, and only stops polling when all input has been read.
This fixes#70#85 and other errors related to parsing large files on STDIN.
For now the implication is that UglifyJS will not leak a function
expression's name in the surrounding scope (IE < 9 does that).
(ref. mishoo/UglifyJS#485)
This is useful while compressing generated code; for example compressing JS
compiled by CoffeeScript (assuming you got a source map):
uglifyjs2 --in-source-map generated.js.map \
--source-map uglified.js.map \
-o uglified.js
The above assumes you have a "generated.js.map" file which is the source
mapping between your CoffeeScript and the generated.js (compiled output from
CoffeeScript). The name of the input file is not present in this example;
it will be fetched from the source map (but it can be passed manually too).
The output will be in "uglified.js" and the output map "uglified.js.map"
will actually map to the original CoffeeScript code, rather than to
generated.js.
- a = a + x ==> a+=x
- joining consecutive var statements (hoisting is not always desirable)
- x == false ==> x == 0, x != true ==> x != 1
- x, x ==> x; x = exp(), x ==> x = exp()
- discarding useless break-s
- all symbols now have a `thedef` property which is a SymbolDef object,
instead of the `uniq` that we had before (pointing to the first occurrence
of the name as declaration).
- for undeclared symbols we still create a SymbolDef object in the toplevel
scope but mark it "undeclared"
- we can now call figure_out_scope after squeezing, which is useful in order
not to mangle names that were dropped by the squeezer
