What is JavaScript? History of appearance and main features

Modern Internet is hard to imagine withoutinteractive web pages. Inconspicuous updating, receiving messages, sending them - all this became commonplace largely due to special scripting languages. This article will focus on what JavaScript is.

Description

JavaScript applies to languages ​​that do not existspecial differences in paradigms. This means that you can write in object-oriented, functional, imperative and other styles. This approach has greatly influenced the simplicity of its study and application. By the way, just for this purpose it was created.

what is javascript

Most likely, the fact of simplicity and functionality andplayed a decisive role in the development and dissemination of the language. It has become so popular that it is used in almost all areas of web programming. JavaScript does not belong to any company. However, the very name of JavaScript is registered for Oracle, which also belongs to Java.

A bit of history

The first attempts to create a new convenient language wereundertaken in 1992 by Nombas. The basis was taken language S. The final version has acquired the name CEnvi. However, this product has not received much distribution. Then the programmer Brendan Eich, Netscape co-founder Mark Andrissen and co-founder Sun Bill Joy took up the case. They cherished the dream of creating a language that could unite all parts of the web interface, and at the same time would be easy to learn and use. The syntax was taken from the fashionable at that time high-level languages ​​- SI and Java.

what is javascript error

During the development of the product several timesrenamed. The initial version was called Mocha, then - LiveScript, and already in the final - JavaScript. In our time, almost every Internet user even remotely knows what JavaScript is.

Language features

What can be done in the JavaScript language,practically unlimited. It is embedded in applications, web pages, services and standalone-products. A new and powerful bundle of AJAX has brought even more opportunities to realize the potential of JavaScript. It is this that makes it possible for a user to update a small part of a page without having to reboot the entire page. This allows you to save traffic and increase the usability of web interfaces.

Application inside web pages

Introduction to the document occurs by specifyingspecial tags, indicating the beginning and end of the script - <script> and </ script>. As a rule, embedding a script directly into HTML-code is considered a mauveton. A more elegant and recognized way is to put the code in a separate file, and then connect it to the right place on the page.

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What is JavaScript in terms of syntax? A typical code might look like this:

<script>

alert (`Hello World!`);

</ script>

This is the simplest implementation, with the help ofwhich you can see the basic elements and their use. Variables are declared in the language by specifying the var keyword and the subsequent name. For example, this is: var variablename.

To assign a value to it, it is usedequal sign. There are 6 known types of variables in JavaScript. This is a number, a string, a Boolean, a null, an undefined, and an object. As a rule, hard type instructions are not required when creating. That is, the variable can take almost any value. More details about the properties of the language can be found in the official manuals on it.

Communication with Java

There is an opinion that the scripting language JavaScriptis related to Java. This is not quite true. They are similar in several aspects - both are object-oriented, have a C-like syntax. Also, languages ​​are actively used to create web applications and services.

what are cookies and javascript

However, the differences are more significant. The implementation of the object-oriented paradigm occurs in Java with the help of classes, and in JavaScript - with prototypes. They differ also by typification. Java compiles into its own special bytecode. JavaScript is interpreted straight from the script.

Known Issues

Security-Related JavaScripttrouble - the use of the so-called XSS type attack. It is based on the implementation of the script in the body of the page, which is displayed to the user. The code can get the rights of the current visitor and use them to harm, for example, steal personal data.

What are cookies and JavaScript? Cookies are a small part of the data that is sent by the web application to the user's computer. It is used to identify visitors, record their preferences or simply store site settings. This can be used by attackers using JavaScript. Having access to the cookies, the hacker can log in to the site under the user's profile and steal personal data. A client application written in JavaScript can undergo reverse development, it is incorrect to pass authorization. Therefore, JavaScript does not provide the means to ensure a decent level of security.

what is javascript void 0

Vulnerabilities and emerging errors canand not through the fault of JavaScript. Many browsers contain potential "holes" in their code. And JavaScript is very often used only as an instrument for using them.

Often on the web, one can come across a question fromusers of social networks: what is a JavaScript error "Vkontakte"? This is a fairly common problem. Its root can be hidden in the old software, cache or in the presence of viruses on the computer. For the treatment you need to try to clear the cache, update Java and Flash on the PC. Also very often people are interested in what is JavaScript void 0. In simple terms, the web developer, for some reason, decided to keep the activity and activity of any link, while leaving it to process events, for example, click on her.

Conclusion

So, what is JavaScript? It is easy to learn and use the scripting language, which is used on almost every website or web service on the Internet. On its basis, libraries are created and promoted that expand the functionality and simplify the development. The standard features of JavaScript are enough to implement most of the tasks related not only to web programming, but also to application solutions.



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