Google Closure Library的基准测试

Question

When I search for performance of Javascript libraries I get many sites showing the comparision of performance between the following popular libraries

• jQuery (pretty slow)
• Prototype(very slow in IE)
• Dojo ( fastest when comes to DOM )
• ExtJs (average)
• Micro JS( slow but OK )

But in any of the benchmarks, Google Closure Library is NOT included. Is it not like any other standard library for it is said that it is a procedural style library.

I need some benchmarks on the performance of Closure library. And would like an advice on "Is switching to Closure library good when using dojo at beginner stage and jQuery at some intermediate stage"

Google posts that it uses the closure library in all its apps like Gmail, etc... The performance is very good. Is this because of the library ? Can an intermediate javaScript coder who can write OO code in JS use Closure library to very high level, or is it advisable to continue using DOJO.

Answer 1

On Closure Library

The Closure Library is pretty close to Dojo in style -- actually, when it was first developed, the authors took inspiration from Dojo.

However, the speed and power of the Closure Library came from the Closure Compiler, which heavily optimizes a JavaScript program in order to remove all the bottlenecks (such as navigating chains of namespaces).

I personally don't like it a single bit as it detracts from the beauty of Dojo class-based constructs (simply to satisfy the compiler) and all those goog.kitchen.sink.getMeACupOfTeaSoICanRelax() long namespaces make writing (and reading) JavaScript programs a royal pain -- the fact that long namespaces are all optimized away by the compiler does not make it pretty (to me) to overuse them because you can .

In addition, its obsession with trying to make JavaScript programs look as much OOP as possible (perhaps because there are tons of Java programmers in Google) means over-reliance on OOP concepts like property getters and setters and the avoidance of many useful (and unique) JavaScript features like mixin's. If you are a Java programmer learning to program in JavaScript, you'll be right at home using the Closure Library. That doesn't make it any bit elegant.

It does, however, offer an industrial strength environment that is rock solid -- since Google has built HUGE sites with it. It is something that (in my personal opinion) is solid and works well, but looks ugly.

However, Dojo is rock solid as well, but more volatile since it is an open-source development project. You decide whether you'd like to switch.

On the Closure Compiler and Dojo

Actually, you can use Dojo with the Closure Compiler in Advanced Mode also. See this link for a description on how to do it. Based on my own tests, a program compiled by the Closure Compiler is typically around 25% smaller than minified versions (due to dead-code elimination) and runs about 20-30% faster for simple pages and more for large pages.

On Speed of Libraries in General

Other libraries all have their own characteristics and quirks, and each balance useability, flexibility and power with performance. For example, jQuery creates many many jQuery objects on the way and has a performance penalty, especially on older browsers. However, modern browsers, esp. Google Chrome, actually does optimizations so that the performance hits of using jQuery is minimal.

You actually need to ask yourself why you need JavaScript to run fast. Most modern browsers are already quite fast so that it is really not a very important consideration regarding choice of library. Better choose your library based on whether it suits you or not (and the task you're at hand) instead of whether it runs 10ms faster in a browser.

If you are writing a web site for mobile devices, or writing an HTML5 game for instance, you may need to squeeze the last drop of performance (in games) and/or save as much resources as possible (in mobile). In such cases, I find that using Dojo and then compiling with the Closure Compiler yields one of the best combinations for such scenarios.

Answer 2

Would be nice to back this up with some data. There's lies, statistics and benchmarks. You may for example ask yourself why framework x is slower then framework y. In general though, benchmarks do not reflect real world scenario's, and end to be fun, but useless. I've worked with jQuery for a few years now and I've not encountered situations where it's slow, or that it had any effect on the usability.

I your code is too slow and you need to optimize it. Then you may benchmark, profile and debug the sweet jesus out of that code. Things like gmail are likely to have had that kind of treatment. So gmail is probably not fast because of closure, but fast because of intelligent programming.

If you're affraid of slow code, you might want to learn generic javascript optimization methods, and you'll be a happy camper with any framework.

edit: on closure Choosing closure might have several advantages when you're building big and complex: there are some nice bandwith optimization tools, tools for managing more complex applications. There is a good guideline on how to write proper code, and tools to check that you followed these guidelines (closure linter, quite interesting). There's a nice templating system (probably won't improve your performance per se) and dependency management stuff. If you wish to integrate these tools, or build upon it, I would say go for it, otherwise, you may rest easy and be happy with your choice for dojo.

Answer 3

using dojo at beginner stage and jQuery at some intermediate stage

You've got that the wrong way around. Dojo is far more advanced than jQuery. jQuery itself is for beginners.

Can an intermediate javaScript coder who can write OO code in JS use Closure library to very high level, or is it advisable to continue using DOJO.

Either library will work. Spend a few hours playing with google closure and see how you find it. I doubt there's that much difference apart from general easy integration with google libraries like google charts.