A brief introduction to JavaScript (Note: Many of the ideas in this article originate from JavaScript advanced programming, if infringing, delete immediately)

JavaScript is the most misunderstood language, the essence of the language and the dross coexist (may be larger than the general language of this proportion); but "Thousand Amoy is laborious, blows the yellow sand beginning to the gold", under the layer veil is the easy-to-use flexible, graceful ethereal inside. A long time ago, JavaScript was used as a toy language until the advent of Ajax until the V8 engine was easy to use; The situation has changed.

JavaScript was born in 1995 (I was very young at that time); a man named Brendan Eich designed the language. He worked for the Netscape company, and he persuaded Mister to develop the language. However only 10 days, 10 days were used. The language was originally used to resolve forms validation operations to be processed by the server-side language (Perl, etc.). Why is it? In the era of "cat" (Modem) dial-up internet, the speed is only 28.8kbit/s ah. You fill out a form or the like if you fill in the wrong or fill in the not filled, you submit data only wait, wait for a half day nothing can do; perhaps the most sad thing is you may be a notice, you fill the wrong AH (heart 10,000 grass mud horse ran). This can be seen in the client to verify how useful it is.

The relationship between JavaScript and Java is like "Lei Feng" and "Leifeng Pagoda". To say there is a relationship, that is the speculation relationship. That year Netscape and Sun (the sun and Java relationship that called a tight) what developed JavaScript, Java is hot, then name it JavaScript. JavaScript is quickly accepted from birth, without rigorous testing by the lab, and the time of completion is short, and the language itself is a lot of problems. The JS1.1 version was introduced in NN4 in 1996, while IE3 has VBScript, but it supports JScript (but the reverse JS1.0). Because there is no standard of fact, there are many inconsistencies between the two. In 1997, a JS1.1-based solution was submitted to ECMA,ECMA to let tc#39 be responsible for implementing a vendor-neutral, generic, cross-platform scripting language syntax and semantics. Tc#39 gave the ECMA-262 standard (for ECMAScript). 1998,iso/iec accepted the standard.

ECMAScript does not define the I/O for the language, so it can be expanded as a core. JavaScript is just one of them, with Adobe ActionScript and so on, server side and node. JavaScript includes: ECMAScript, DOM, BOM.

What does the ECMAScript define? Syntax, statement, type, keyword, reserved word, object, operator. ECMAScript defines its compatibility: 1, to support Unicode (support for multilingual development)2, support defined types, values, objects, attributes, functions, syntax, etc. 3, you can extend undefined types, values, objects, properties, functions, syntax, etc. 4, Supports support for undefined regular expressions, programs. is still relatively open. For its support, JS1.1 and JS1.2 do not fully support ECMAScript 1; JS1.3 is the first fully supported one. IE3 the support, but in fact it is not so! JS1.4 also only supports server side, and the successor of NN begins with version number JS1.5. In general, browser compatibility is measured with support for ECMAScript and Dom, because naming rules are confusing.

Ecmasript has a version 6, and the first version supports Unicode on a JS1.1 basis and supports platform-independent objects. The second edition of the Agreement with ISO/IEC only made some editorial work. New in the third edition: Processing of strings, regular expressions, new control statements, Try-catch statements, error types, numeric outputs. The fourth edition was abandoned because the gap with the third edition was too large to replace it with the following 3.1 scenario (ECMAScript 5). Version fifth supports native JSON objects, inheritance, and advanced properties, and contains a strict pattern that complements the engine interpretation execution code.

DOM (Document Object model, published in 1998): For XML and extended to HTML-generic, cross-platform APIs. It maps the document structure to a multi-layered structure. The advent of the DOM in order to deal with IE and the same time NN of a single big. They make the concept of DHTML, but they are different. This makes it necessary to write multiple documents across platforms. But in fact the DOM is not clear. At present the DOM is divided into three levels, the DOM0 level refers to the historical concept of the respective support for DHTML at that time.

1.DOM Level1: Contains core (implementing XML Document Mapping), HTML (core-based extensions, objects, methods).

2.DOM Level2:core extension to namespace support, add views, Events, Style, Range, and traversal modules.

The 3.DOM Level3:core supports XML1.0 (XML Infoset, XML Xpath, XML Base) and adds the load and Save, validation module.

Other languages also support SVG, Mathxml, SMIL. IE5 started to support the DOM, but IE5.5 fully supported it, IE6, 7 in laurels, IE8 fix BUG,IE8 the first to start supporting ECMASRIPT5,IE9 has fully supported (Microsoft still has progress).

BOM (Browser object model)

The BOM only supports the operation of frames and windows, but it also puts some other browser-specific actions in it, such as:

1. Popup new window, 2, move, Close, Zoom window, 3, support for Cookie, 4, Support Navigator object, 5, Support screen object, 6, support location;7, custom XMLHttpRequest and ActiveXObject.

The original BOM is closely related to the browser, and different browsers have different implementations. HTML5 to the norm. Finish

A brief introduction to JavaScript (Note: Many of the ideas in this article originate from JavaScript advanced programming, if infringing, delete immediately)