#closure compiler

O Google Closure Compiler é uma das ferramentas mais robustas já desenvolvidas para a minificação e otimização avançada de código JavaScript (JS). Criado pelo Google, seu objetivo vai além de simplesmente reduzir o tamanho dos arquivos: ele também realiza análises semânticas, otimizações inteligentes, reestruturação de funções e até mesmo verificações avançadas de erros, ajudando desenvolvedores…

When using ADVANCED_OPTIMIZATIONS in Google Closure Compiler (cc), I saw that it polluted the global scope with variables such as a, c, e, f, ...

The solution is really plain and simple. Expose the API as usual with window['method_name'] = some.method; and create an IIFE around the compiled/minified cc-product.

!function(a) { .... cc product goes here ... }(window);

If you use a reference to window in your code, you will also typically see a shortcut to window as one of the first declarations in the cc product (var a = window, ...). You can simply remove this by sending in window as an argument, as you see in my example above.

The Google Closure Compiler (online service here) is a great tool to optimize (shrink) javavascript code, reducing the files size for faster loading. It has 3 optimization levels, to suit your needs (whitespaces only, simple and advanced. The first 2 optimization levels are kinda straight forward, but the advanced mode (best optimizations) needs some adjustments in your code. 

it detects unused code, so if you are trying to optimize a library that only has functions that are used somewhere else, you will end up with an empty result (nothing is used). The solution for this can be found here:

function displayNoteTitle(note) { alert(note['myTitle']); } // Store the function in a global property referenced by a string: window['displayNoteTitle'] = displayNoteTitle;

it is very picky about undeclared functions. If you are trying to optimize a library that uses jQuery, it will rename calls to methods it does not know, so $('#abc').text('text');becomes something like $('#abc').a('text');. The solution for that is to declare an externs url for the jQuery library. On the online service, that can be done by using the following header

// ==ClosureCompiler== // @compilation_level ADVANCED_OPTIMIZATIONS // @output_file_name default.js // @externs_url https://closure-compiler.googlecode.com/git/contrib/externs/jquery-1.9.js // ==/ClosureCompiler== // ADD YOUR CODE HERE

Other useful pieces of information about Closure Compiler:

Closure Compiler опять жгёт.

return (true)

Хха.