YUI Compressor: What are micro optimizations?


YUI Compressor, in its (not very extensive) documentation states this as an option:

--disable-optimizations Disable all the built-in micro optimizations.

Does anyone know what this means?<br /> What will this turn on/off?<br /> I haven't found any documentation about it.



Looking at the source of JavaScriptCompressor:

<a href="https://github.com/yui/yuicompressor/blob/master/src/com/yahoo/platform/yui/compressor/JavaScriptCompressor.java#L548" rel="nofollow">lines 548</a>-

if (!disableOptimizations) { optimizeObjectMemberAccess(this.tokens); optimizeObjLitMemberDecl(this.tokens); }

<a href="https://github.com/yui/yuicompressor/blob/master/src/com/yahoo/platform/yui/compressor/JavaScriptCompressor.java#L467" rel="nofollow">lines 467</a> -

/* * Transforms obj["foo"] into obj.foo whenever possible, saving 3 bytes. */ private static void optimizeObjectMemberAccess(ArrayList tokens) {

<a href="https://github.com/yui/yuicompressor/blob/master/src/com/yahoo/platform/yui/compressor/JavaScriptCompressor.java#L497" rel="nofollow">lines 497</a> -

/* * Transforms 'foo': ... into foo: ... whenever possible, saving 2 bytes. */ private static void optimizeObjLitMemberDecl(ArrayList tokens) {

So it's converting use of constant strings in foo['bar'] to foo.bar and {'bar':x} to {bar:x}.


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