Closure Tools. The compiler removes dead code and rewrites and minimizes what's left so that it downloads and runs quickly. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. These checks and optimizations help you write apps that are less buggy and easier to maintain. If hello. Now that we have created a giant heap of JavaScript, it is time to shrink it down using the Closure Compiler. Even though calcdeps. Make sure that the Closure Compiler jar is available at..
This command compiles hello. Now that hello-compiled. Unfortunately, loading hello-compiled. Instead, it yields a JavaScript error: example is not defined.
The simplest solution is to make sure that example. The Compiler must be run again on the updated version of hello. Once hello-compiled. However, now that hello-compiled. Looking at hello-compiled. Most of that logic deals with browser and platform detection that can be eliminated by specifying the target environment at compile time.
In the following code, additional flags are used to specify a Gecko-based browser running on Windows, which removes almost a kilobyte from the compiled code:. This runs the Compiler in Advanced mode , the mechanics of which are explained in great detail in Chapter For now, the only thing you have to know about Advanced mode is that it is able to dramatically optimize JavaScript code written in a particular style, so many of the upcoming chapters on the Closure Library will cite Advanced mode as the reason why code is written in a certain way.
After reading all of the chapters on the Closure Library, you will be able to fully appreciate all of the optimizations that the Compiler can perform in Advanced mode. Although the code appears to work fine when run in the browser, it is a good idea to create a unit test to ensure the correct behavior is preserved.
In this case, example. Note how information is also logged to the Firebug console while the test is running to help with debugging. Because the Closure Inspector is used to help with debugging compiled JavaScript, hello. Though rather than create an actual bug, simply insert a debugger statement in hello. Because hello. In addition to hello-compiled. Although the data in hello-map may look like JavaScript, only its individual lines are valid JSON, not the file as a whole.
When a web page hits a debugger statement while a JavaScript debugger is enabled, such as Firebug, the program will suspend so that the program state can be inspected using the debugger.
Reloading hello-compiled. When you use the Closure Inspector for the first time, it will also ask you to choose a file where your settings for the Inspector can be saved. Something like inspector-settings. Once you have set the source map in the Inspector, refresh hello-compiled.
By using the deobfuscated stack trace provided by the Closure Inspector, it is possible to look at the program and determine where the current point of execution is. Chapter 16 contains more information about the Inspector.
Skip to main content. Start your free trial. Chapter 1. Introduction to Closure. Tools Overview. Closure Library. Closure Templates. Closure Compiler. Closure Testing Framework. Closure Inspector. Closure Design Goals and Principles. Managing Memory Matters.
Code Must Work Without Compilation. Code Must Be Browser-Agnostic. Code Must Work Across Frames. Tools Should Be Independent. Downloading and Installing the Tools. Tip Because all of the Closure Tools are designed to be used independently, it takes a bit of effort to get them set up and working together.
Table Revision numbers for Closure Tools used to produce the examples in this book. Each is the latest version as of July 4, Clearly, some of the tools are updated more frequently than others. Find centralized, trusted content and collaborate around the technologies you use most. Connect and share knowledge within a single location that is structured and easy to search.
Look at this question for the detailed reason of why I'm using Google Closure Template. I want it to be multilingual. I see that there is a --locales switch and also looked at the samples provided in the project here and here. We need both simple. Note: For an example Ant target and command line args that generates these files, please see target 'js-features-example' within the top-level 'build. What I expected was that it would generate just one JavaScript code base which will use desired strings from the appropriate locale file based on an option provided at runtime before the template function is called.
Is that possible with closure templates? This object can be generated on the server-side from your locale file and transfered to javascript via script tag. Otherwise you can load different compiled template file to the client side according to the locale. There's also i18n possibility , but it's kinda useless for your problem, imo. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Is the compiler also effective in optimizing code written for existing libraries like jQuery, prototypejs, scriptaculous, mootools, etc?
Great news! Now I won't be able to see the source code on the web and learn anymore! Awesome stuff! A few questions regarding GWT vs. Closure - 1. Does it makes sense for GWT developers to look at Closure? Congratulations everybody! Funny to see a UI library from Google. While your products and sites are known to be functional and compatible, they are also famous for being among the ugliest from a design and UI perspective. Denis Sokolov : I'm sure they're quite aware of Packer. While packer is useful for obsfuscation, you do not gain much by the compression.
The way it works, using eval and string substitution, exchanges computation time for file size. This gives poor performance where it counts, on netbooks, IE6 or phones. Packer is only useful for compression when saving bandwidth is more critical than reducing execution time, i. I could not understand that. Amazing stuff! Shelby Pratt I am sure they are aware of it as well. I am pretty sure, that you, as well as I, have not calculated the exact loss of execution time versus download time the packer provides.
Obviously, the results may be that the execution time loss is huge. In that case, surely packer is the wrong choice. However, it might be that the time needed to unpack the script is very very short. In that case, 0. Now, shall we perform real tests on packer'ed code, what do you think?
However, I am afraid that eval is not very scientific. Hello there.
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