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In short, you write, test and debug your client-side code in Java and let GWT cross-compiler convert it all into cross-browser JavaScript. When compiled the Client-side is now pure JavaScript and HTML.
With GWT you "
Only pay for what you use!
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The GWT Cross-Compiler prunes unused classes, methods and attributes, from your code. In addition, the Cross-compiler compresses the JS naming and obsfuscates your code to the shortest possible length.
In fact, GWT can generate faster JavaScript than you can write by hand!
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