JavaScript as Compilation Target: ClojureScript and Dart – #programming #bookreview

Despite its widespread success, JavaScript has a reputation for being a computer language with many flaws. Still, it is now everywhere on the planet, so it is here to stay, very likely for a long, long time.

Not surprisingly, several new languages have emerged that jump over some of JavaScript’s hurdles, offer improved capabilities, and also compile to optimized JavaScript code.

Two of these languages are the focus of noteworthy new “Up and Running” books from O’Reilly: ClojureScript: Up and Running and Dart: Up and Running.

Here are short reviews of each book:

ClojureScript: Up and Running
Stuart Sierra and Luke VanderHart
(O’Reilly, paperback, Kindle)

ClojureScript, the authors contend, “provides developers with a language that is more powerful than JavaScript, which can reach all the same places JavaScript can, with fewer of JavaScript’s shortcomings.”

The primary targets of ClojureScript are “web browser applications, but it is also applicable to any environment where JavaScript is the only programmable technology available,” they add.

“ClojureScript is more than Clojure syntax layered on top of JavaScript: it supports the full semantics of the Clojure language, including immutable data structures, lazy sequences, first-class functions, and macros,” they emphasize.

Their 100-page book focuses on how to use ClojureScript’s features, starting at the “Hello world” level and gradually advancing to “Development Process and Workflow” and “Integrating with Clojure.” (ClojureScript is designed for building client-side applications, but it can be merged with Clojure on the JVM to create client-server applications.)

Early in the book, they also describe how to compile a ClojureScript file to JavaScript and emit code “that is fully compatible with the Advanced Optimizations mode of the Google Closure Compiler.”

The two writers are Clojure/ClojureScript developers with a previous book to their credit.

ClojureScript: Up and Running is written well and appropriately illustrated with code samples, flow charts, and other diagrams. The authors recommend using the Leiningen build system for Clojure, plus the lein-cljsbuild plug-in for ClojureScript.

Their book is a smooth introduction to ClojureScript that requires no prior knowledge of Clojure. But you do need a basic working knowledge of JavaScript, HTML, CSS, and the Document Object Model (DOM).

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Dart: Up and Running
Kathy Walrath and Seth Ladd
(O’Reilly, paperback, Kindle)

Google created Dart to be “an open-source, batteries-included developer platform for building structured HTML5 web apps,” the two authors note.

Dart provides not only a new language, but libraries, an editor, a virtual machine (VM), a browser that can run Dart apps natively, and a compiler to JavaScript.”

Indeed, Dart looks very similar to JavaScript and is “easy to learn,” the two writers state. “A wide range of developers can learn Dart quickly. It’s an object-oriented language with classes, single inheritance, lexical scope, top-level functions, and a familiar syntax. Most developers are up and running with Dart in just a few hours.”

The authors work at Google and note that some of the software engineers who helped develop the V8 JavaScript engine that is “responsible for much of Chrome’s speed” are now “working on the Dart project.”

Dart has been designed to scale from simple scripts all the way up to complex apps, and it can run on both the client and the server.

Those who choose to code with Dart are urged to download the open-source Dart Editor tool, because it also comes with a “Dart-to-JavaScript compiler and a version of Chromium (nicknamed Dartium) that includes the Dart VM.”

Since Dart is new, the writers also urge readers to keep an eye periodically on the Dart website and on their book’s GitHub site, where code can be downloaded and errors and corrections noted.

Dart: Up and Running is a well-structured, well-written how-to book, nicely fortified with short code examples and other illustrations. While the book appears very approachable and simple, it is not for complete beginners. You should have a basic working knowledge of JavaScript, HTML, CSS, and the Document Object Model (DOM).

If you are looking for a web development language that matches JavaScript’s dynamic nature but also addresses JavaScript’s sometimes-aggravating shortcomings, consider trying Dart—with this book in hand.

Si Dunn

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