What is javascript mainly used to solve?

Javascript is mainly to solve the speed problem left by server-side languages ​​and provide customers with a smoother browsing effect. At that time, the server needed to verify the data. Since the network speed was quite slow, the verification step wasted too much time; so Netscape developed Javascript to provide the basic function of data verification.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

Javascript is a prototype-inherited, object-oriented, dynamically typed, case-sensitive client-side scripting language developed from Netscape's LiveScript. The main purpose is to Solve the speed problems left by server-side languages, such as Perl, and provide customers with smoother browsing effects.

At that time, the server needed to verify the data. Since the network speed was very slow, only 28.8kbps, the verification step wasted too much time. So Netscape's browser Navigator added Javascript to provide basic functions of data verification.

Background of the birth of JavaScript

In the 1990s, web programs in European and American countries became increasingly popular, but at that time, users were still using them when surfing the Internet. Telephone dial-up Internet access, through modem, the Internet speed is only 28kb/s. The display of web programs is becoming increasingly rich. In the days before JavaScript, form validation and other operations were performed on the server side.

For example, the user enters a registration page, fills in the user name, password, personal information, clicks to register, okay, it’s a big deal. . .

Send information and start network transmission. After waiting for more than ten seconds, the server receives the information sent by the browser client, starts processing, and then returns the processed information to the client browser. The user suddenly finds that he is prompted to fill in the user name. To start with a capital letter, modify it and click Register. . .

Then repeat the previous step, and finally it prompts that the password is too short and not secure enough. Just a simple registration page can take a lot of time in form validation and waste bandwidth. This is unbearable for users.

In this context, society urgently needs a client language to solve such problems. Netscape, which was at the forefront of technology at the time, began to develop a client-side scripting language.

1995 Brandon Aitch, who worked at Netscape, developed a scripting language called LiveScript in Netscape Browser 2.0. In order to catch up with the media's enthusiasm for Java, it was renamed JavaScript. From then on JavaScript was born.

JavaScript Standardization

People are afraid of being famous and pigs are afraid of being strong. Once JavaScript was launched, it attracted widespread attention in society. Different versions of the JavaScript language came out one after another. The popular ones at that time were: JavaScript in Netscape Navigator 3.0, JScript in IE, and ScriptEase in CEnvi. For programmers, if they want to develop a user-friendly web program, compatibility may be a big workload. After all, some users use different browsers and have different embedded scripting languages. The standardization of JavaScript comes to the fore.

In 1997, some scientists and programmers from Sun, Microsoft, etc. sat together for a meeting and formulated the ECMA-262 standard to standardize ECMAScript. From then on, major browser manufacturers used ECMAScript as JavaScript The basis for implementation.

Composition of JavaScript

JavaScript consists of three parts: ECMAScript, BOM, and DOM. ECMAScript is the core of JavaScript and specifies JavaScript variables. , types, keywords, functions and other basic languages. DOM is a document operation object, which is an interface for operating HTML and XML elements; BOM is a browser object, which can access and operate the browser window.

The ECMA262 standard only defines the ECMAScriptd standard for DOM. There is no standard for BOM. BOM and DOM belong to host objects.

The so-called host is the running environment of JavaScript, such as the browser you see now. Different browsers have slightly different views on host objects, so the most painful compatibility issues faced by front-end developers are mainly caused by BOM and DOM.

What JS can do

JavaScript can be used in various areas of web development, such as:

• Web application development: The web pages we browse in daily life are composed of HTML, CSS, and JavaScript. Through JavaScript, the styles of elements in the web page can be updated in real time, and the interaction between people and web pages can be realized (such as monitoring users Whether the mouse is clicked or a key is pressed, etc.), you can also add some cool animations to the web page;

• Mobile application development: In addition to web application development, JavaScript can also be used to develop applications on mobile phones or tablets, and we can also use some excellent frameworks (such as React Native) to make development easier;

• Web Games: The small games we have played on the web can all be implemented using JavaScript;

• Back-end Web application development: In the past, we used JavaScript to develop the front-end part of Web applications, but with the emergence of Node.JS (a JavaScript runtime environment), JavaScript can also be used Used to develop the backend part of web applications.

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