The Name

The Java- prefix suggests that JavaScript is somehow related to Java,
that it is a subset or less capable version of Java. It seems that the name
was intentionally selected to create confusion, and from confusion comes misunderstanding.
JavaScript is not interpreted Java. Java is interpreted Java. JavaScript is
a different language.

JavaScript has a syntactic similarity to Java, much as Java has to
C. But it is no more a subset of Java than Java is a subset of C. It
is better than Java in the applications that Java (fka Oak)
was originally intended for.

JavaScript was not developed at Sun Microsystems, the home of
Java. JavaScript was developed at Netscape. It was originally called
LiveScript, but that name wasn't confusing enough.

The -Script suffix suggests that it is not a real programming language,
that a scripting language is less than a programming language. But it is really
a matter of specialization. Compared to C, JavaScript trades performance for
expressive power and dynamism.

Lisp in C's Clothing

JavaScript's C-like syntax, including curly braces and the
clunky for statement, makes it appear to be an ordinary
procedural language. This is misleading because JavaScript has more
in common with functional languages like Lisp or Scheme than with C or Java.
It has arrays instead of lists and objects instead of property
lists. Functions are first class. It has closures.
You get lambdas without having to balance all those parens.

Typecasting

JavaScript was designed to run in Netscape Navigator. Its success there led
to it becoming standard equipment in virtually all web browsers. This has resulted
in typecasting. JavaScript is the
George Reeves of programming languages. JavaScript is well suited to a large
class of non-Web-related applications

Moving Target

The first versions of JavaScript were quite weak. They lacked
exception handling, inner functions, and inheritance. In its present
form, it is now a complete object-oriented programming language. But
many opinions of the language are based on its immature forms.

The ECMA committee that has stewardship over the language is
developing extensions which, while well intentioned, will aggravate
one of the language's biggest problems: There are already too many
versions. This creates confusion.

Design Errors

No programming language is perfect. JavaScript has its share of design errors,
such as the overloading of + to mean both addition and concatenation
with type coercion, and the error-prone with statement should be avoided.
The reserved word policies are much too strict. Semicolon insertion was a huge
mistake, as was the notation for literal regular expressions. These mistakes
have led to programming errors, and called the design of the language as a whole
into question. Fortunately, many of these problems can be mitigated with a good
lint
program.

The design of the language on the whole is quite sound.
Surprisingly, the ECMAScript committee does not appear to be
interested in correcting these problems. Perhaps they are
more interested in making new ones.

Lousy Implementations

Some of the earlier implementations of JavaScript were quite buggy. This reflected
badly on the language. Compounding that, those implementations were embedded
in horribly buggy web browsers.

Bad Books

Nearly all of the books about JavaScript are quite awful. They contain errors,
poor examples, and promote bad practices. Important features of the language
are often explained poorly, or left out entirely. I have reviewed dozens of
JavaScript books, and I can only recommend one: JavaScript:
The Definitive Guide (5th Edition) by David Flanagan. (Attention authors:
If you have written a good one, please send me a review copy.)

Substandard Standard

The official
specification for the language is published by ECMA.
The specification is of extremely poor quality. It is difficult to read and
very difficult to understand. This has been a contributor to the Bad Book problem
because authors have been unable to use the standard document to improve their
own understanding of the language. ECMA and the TC39 committee should be deeply
embarrassed.

Amateurs

Most of the people writing in JavaScript are not programmers. They
lack the training and discipline to write good programs. JavaScript
has so much expressive power that they are able to do useful things
in it, anyway. This has given JavaScript a reputation of being
strictly for the amateurs, that it is not suitable for professional
programming. This is simply not the case.

Object-Oriented

Is JavaScript object-oriented? It has objects which can contain
data and methods that act upon that data. Objects can contain other
objects. It does not have classes, but it does have constructors
which do what classes do, including acting as containers for class
variables and methods. It does not have class-oriented inheritance,
but it does have prototype-oriented inheritance.

The two main ways of building up object systems are by inheritance
(is-a) and by aggregation (has-a). JavaScript does both, but its
dynamic nature allows it to excel at aggregation.

Some argue that JavaScript is not truly object oriented because it
does not provide information hiding. That is, objects cannot have
private variables and private methods: All members are public.

But it turns out
that JavaScript
objects can have private variables and private methods. (Click here now
to find out how.) Of course, few understand this because JavaScript is
the world's most misunderstood programming language.
Some argue that JavaScript is not truly object oriented because it does not
provide inheritance. But it turns out that JavaScript
supports not only classical inheritance, but other code reuse patterns as well.

My Blog

 copied 
Douglas
Crockford

www.crockford. com

[Non-text portions of this message have been removed]