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Javascript is a dynamic language, a dynamically typed, weakly typed, prototype-based language; javascript can respond to user input without going through a Web server.

This article operating environment: windows7 system, javascript1.8.5 version, Dell G3 computer.

Is javascript a dynamic language?

JavaScript is a dynamically typed, weakly typed, prototype-based language. Its interpreter, known as the JavaScript engine, is a part of the browser and is widely used in the client scripting language. It was first used on HTML pages to add dynamic functions to HTML pages.

The JavaScript scripting language has the following characteristics:

(1) script language. JavaScript is an interpreted scripting language. Languages such as C and C++ are compiled and then executed, while JavaScript is explained line by line in the process of running the program.

(2) based on object. JavaScript is an object-based scripting language that can not only create objects, but also use existing objects.

(3) simple. The JavaScript language uses weak variable types and does not make strict requirements on the data types used. It is a scripting language based on Java basic statements and control, and its design is simple and compact.

(4) dynamic. JavaScript is an event-driven scripting language that responds to user input without going through a Web server. When visiting a web page, JavaScript can directly respond to these events when the mouse clicks or moves up and down, window movement and other operations in the web page.

(5) Cross-platform. The JavaScript scripting language does not depend on the operating system and only needs the support of browsers. So a JavaScript script can be written and used on any machine, as long as the browser on the machine supports the JavaScript scripting language, and JavaScript is already supported by most browsers. [6] unlike server-side scripting languages, such as PHP and ASP,JavaScript, are mainly run on users' browsers as client-side scripting languages and do not require server support. So in the early days, programmers preferred JavaScript to reduce the burden on the server, while at the same time brought another problem, security.

With the strength of the server, although programmers prefer to run scripts on the server side to ensure security, JavaScript is still popular for its cross-platform, easy-to-use and other advantages. At the same time, some special features, such as AJAX, must be supported on the client side by relying on JavaScript.

Programming languages can be divided into two categories according to data types, one is statically typed language, the other is dynamically typed language.

A statically typed language determines the type of a variable at compile time, while a dynamically typed language does not have a type until the variable is assigned a value when the program is running.

Advantages of statically typed languages:

1. Errors with mismatched types can be found at compile time, and the editor can help us avoid some errors that may occur during the run of the program in advance.

2. If the data type is clearly defined in the program, the compiler can also optimize the program according to this information to improve the execution speed of the program.

Disadvantages of statically typed languages:

1. Forcing programmers to write programs according to strong contracts and specifying data types for each variable, in the final analysis, is only a means to assist us in writing programs with high reliability, not the purpose of writing programs. after all, most people write programs to complete the delivery of production requirements.

2. Type declarations also add more code, and these details distract programmers from thinking about business logic during programming.

Advantages of dynamically typed languages:

Less code is written and looks more concise, so programmers can focus more on business logic. Although not distinguishing types can make a program difficult to understand in some cases, on the whole, the less code and the more focused on logical expression, the more helpful it is to read the program.

Disadvantages of dynamically typed languages:

The type of the variable cannot be guaranteed, so type-related errors may occur during the run time of the program. It's like buying a bag of spicy beef gluten in the store, but you don't know if it tastes like beef until you really eat it.

Javascript is a dynamic language. In JavaScript, when assigning a value to a variable, you don't need to consider its type, so JavaScript is a typical dynamically typed language.

The tolerance of variable types in dynamically typed languages brings great flexibility to actual coding. Since there is no need for type checking, we can try to call any method of any object, regardless of whether it was originally designed to own the method.

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