Why Java Developers Hate JavaScript

As a Java developer, I used to hate JavaScript. At one time I used to say “friends don’t let friends use JavaScript”.

In recent years, JavaScript has become required for a flexible & feature rich user experience. WIth the advent of tools such as JQuery and GWT many of these issues have been minimized. Also, I took the time to read more about JavaScript. The book that really opened my eyes is JavaScript: The Good Parts.

So… What do Java developers hate?

• JavaScript may look like Java, smell like Java and even taste a little like Java, but it does not behave like Java
  
• Variables are global in scope
• “this” has different meaning based on the invocation type (learn this for your own sake)
  
• Braces do NOT guarantee scope
• Functions are first class citizens, not classes (avoid classes, you will set yourself up for disappointment)
  
• Functions are objects, not simply methods to a class
• Variables are dynamically typed objects
• JavaScript often fails silently (this is for user experience)
• Difficult to debug (use FireFox & Firebug addon)
• Semicolons are optional (bad idea, put them where you want them)
• Functions always return values, a value or “undefined”
• “new” has some specific assumptions, not simply creating an Object
• Cross browser compatibility (use jQuery or GWT to address most issues)

What should you understand about JavaScript?

• Functions – First class citizens, the primary object in JavaScript
  
• prototype system – Object.prototoype, object linkage, delegation, hasOwnProperty() method, etc.
  
• closures
• currying
• the 4 invocation types: method, function, constructor & apply
• dynamic languages such as groovy, ruby, etc. they share many similarities

What should you forget when using JavaScript?

• Classes
• Scope using braces
• Strong typing

In summary, it is an entirely different language with many syntactical similarities. JavaScript is very power and flexible once you understand how it behaves. I highly recommend the O’Reilly book (mentioned above), its a short read and packed with awesome facts.

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