Javascript was developed by Netscape. JavaScript was originally designed by Brendan Eich of Netscape, who initially named their scripting language LiveScript, but Netscape later renamed it JavaScript after collaborating with Sun.
The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.
JavaScript ("JS" for short) is a lightweight, interpreted or just-in-time compiled programming language with function priority. Although it is famous as a scripting language for developing Web pages, it is also used in many non-browser environments. JavaScript is a dynamic scripting language based on prototype programming, multi-paradigm, and supports object-oriented, imperative and declarative (such as functional programming) style.
Background of JavaScript
JavaScript was first designed and implemented in 1995 by Brendan Eich of Netscape Company on the Netscape Navigator browser. Its scripting language was originally named LiveScript because Netscape was working with Sun and Netscape management wanted it to look like Java, so it was renamed JavaScript.
JavaScript was originally inspired by Java and was designed. One of the purposes is to "look like Java", so there are similarities in syntax. Some names and naming conventions are also borrowed from Java, but the main design of JavaScript The principle comes from Self and Scheme. The similarity in names between JavaScript and Java was the result of Netscape reaching an agreement with Sun Microsystems for marketing reasons at the time. Microsoft also launched JScript at the same time to compete with the JavaScript scripting language.
In the early days of development, the standard of JavaScript was not yet determined. During the same period, there were three pillars: Netscape's JavaScript, Microsoft's JScript and CEnvi's ScriptEase. For interoperability, Ecma International (formerly the European Computer Manufacturers Association) created the ECMA-262 standard (ECMAScript), both of which are implementations of ECMAScript, although JavaScript is intended as a scripting language for non-programmers, not as a programmer People use scripting languages to promote and advertise, but JavaScript has very rich features.
In 1997, under the coordination of ECMA (European Computer Manufacturers Association), a working group composed of Netscape, Sun, Microsoft, and Borland determined a unified standard: ECMA-262. The complete JavaScript implementation consists of three parts: ECMAScript, Document Object Model, and Browser Object Model. JavaScript has become one of the most famous implementations of ECMAScript.
In addition, ActionScript and JScript are also implementation languages of the ECMAScript specification. Although JavaScript is promoted and advertised as a scripting language for non-programmers rather than as a scripting language for programmers, JavaScript is very rich in features.
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JavaScript script language has the following characteristics:
(1)Scripting language. JavaScript is an interpreted scripting language. Languages such as C and C are compiled first and then executed, while JavaScript is interpreted line by line during the running of the program.
(2) Based on objects. JavaScript is an object-based scripting language that can not only create objects but also use existing objects.
(3)Simple. The JavaScript language uses weakly typed variable types and does not impose strict requirements on the data types used. It is a scripting language based on Java's basic statements and controls, and its design is simple and compact.
(4)Dynamic. JavaScript is an event-driven scripting language that can respond to user input without going through a Web server. When visiting a web page, JavaScript can directly respond to these events when the mouse is clicked, moved up or down, or moved in the window.
(5) Cross-platform. The JavaScript scripting language does not depend on the operating system and only requires browser support. Therefore, after writing a JavaScript script, it can be brought to any machine for use, provided that the browser on the machine supports the JavaScript scripting language. JavaScript has been supported by most browsers. [6] Unlike server-side scripting languages, such as PHP and ASP, JavaScript is mainly used as a client-side scripting language to run on the user's browser and does not require server support. Therefore, in the early days, programmers preferred JavaScript to reduce the burden on the server, but at the same time it also brought about another problem, security.
As servers become more powerful, although programmers prefer scripts running on the server to ensure security, JavaScript is still popular for its cross-platform and easy-to-use advantages. At the same time, some special functions (such as AJAX) must rely on JavaScript to be supported on the client side.
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