The difference between java and js

Although JavaScript and Java are closely related, they are two different products developed by the two companies.

Java is a new generation of object-oriented programming language launched by SUN Company, which is particularly suitable for Internet application development; JavaScript is a product of Netscape Company, and its purpose is to expand the functions of Netscape Navigator. An object-based and event-driven interpreted language that can be embedded in Web pages. Its predecessor is Live Script; and the predecessor of Java is Oak language.

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The following is a comparison of the similarities and differences between the two languages:

Object-based and object-oriented

Java is a true object-oriented language. Even to develop simple programs, objects must be designed.

JavaScript is a scripting language that can be used to create complex software that has nothing to do with the network and interacts with users. It is an Object Based and Event Driver programming language. Therefore it itself provides a very rich set of internal objects for designers to use.

Interpretation and Compilation

The two languages ​​are executed differently in their browsers. Java source code must be compiled before being passed to the client for execution. Therefore, the client must have an emulator or interpreter on the corresponding platform. It can compile the code independently of a specific platform through the compiler or interpreter. of bondage.

JavaScript is an interpreted programming language. Its source code does not need to be compiled before being sent to the client for execution. Instead, character codes in text format are sent to the client for interpretation and execution by the browser.

Strong variables and weak variables

The variables used in the two languages ​​​​are different.

Java uses strong type variable checking, that is, all variables must be declared before compilation. For example:

Integer x;
String y;
x=1234;
x=4321;

X=1234 indicates an integer, and Y=4321 indicates a string.

Variable declaration in JavaScript adopts its weak type. That is, the variable does not need to be declared before use, but the interpreter checks its data type at runtime, such as:

x=1234;
y＝"4321";

The former indicates that x is a numeric variable, while the latter indicates that y is a character variable. variable.

The code format is different

Java is a format that has nothing to do with HTML. It must be loaded by referencing foreign media in HTML, and its code is in byte code The form is saved in a separate document.

JavaScript code is a text character format that can be directly embedded in HTML documents and can be loaded dynamically. Writing HTML documents is as easy as editing text files.

The embedding methods are different

In the HTML document, the two programming languages ​​have different identifiers. JavaScript uses 2934a685527f5cd6bcb20a3dc28499e1...bedae1ad67868425befe4a2056d27ff6 Identification, while Java uses 082dedeb30a00d0e6e2cdb74a392fac3...0f47783e45a827c89a02ecd1506bec99 for identification.

Static binding and dynamic binding

Java uses static binding, that is, Java object references must be made at compile time so that the compiler can achieve strong Type checking.

JavaScript uses dynamic binding, that is, JavaScript object references are checked at runtime. Without compilation, the object reference cannot be checked.

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