Java vs JavaScript

The Differences between Java and JavaScript

Many people use the words Java and JavaScript interchangeably, or confuse the two.

The JavaScript language resembles Java, but without Java's static typing and strong type checking. JavaScript supports most of Java's expression syntax and basic control flow constructs. In contrast to Java's compile-time system of classes built by declarations, JavaScript supports a run-time system based on a small number of data types representing numeric, Boolean, and string values. JavaScript has a simple instance-based object model that still provides significant capabilities.

JavaScript also supports functions, again without any special declarative requirements. Functions can be properties of objects, executing as loosely typed methods.

JavaScript complements Java by exposing useful properties of Java applets to script authors. JavaScript statements can get and set exposed properties to query the state or alter the performance of an applet or plug-in.

Java is an extension language designed, in particular, for fast execution and type safety. Type safety is reflected by being unable to cast a Java int into an object reference or to get at private memory by corrupting Java bytecodes.

Java programs consist exclusively of classes and their methods. Java's requirements for declaring classes, writing methods, and ensuring type safety make programming more complex than JavaScript authoring. Java's inheritance and strong typing also tend to require tightly coupled object hierarchies.

In contrast, JavaScript descends in spirit from a line of smaller, dynamically typed languages like HyperTalk and dBASE. These scripting languages offer programming tools to a much wider audience because of their easier syntax, specialized built-in functionality, and minimal requirements for object creation.

The following table compares and contrasts JavaScript and Java.

JavaScript	Java
Interpreted (not compiled) by client.	Compiled on server before execution on client.
Object-based. Code uses built-in, extensible objects, but no classes or inheritance.	Object-oriented. Applets consist of object classes with inheritance.
Code integrated with, and embedded in, HTML.	Applets distinct from HTML (accessed from HTML pages).
Variable data types not declared (loose typing).	Variable data types must be declared (strong typing).
Dynamic binding. Object references checked at run-time.	Static binding. Object references must exist at compile-time.
Cannot automatically write to hard disk.	Cannot automatically write to hard disk.