What is HTML5

1. What is HTML5

The predecessor of HTML 5 draft is called Web Applications 1.0. It was proposed by WHATWG in 2004, and then accepted by W3C in 2007, and established New HTML working team. On January 22, 2008, the first official draft was released. WHATWG stated that the specification is still a work in progress and requires many years of hard work. Currently, Firefox, Google Chrome, Opera, Safari (version 4 and above), and Internet Explorer 9 support HTML5 technology.

The essence of HTML5 does not completely change the specifications of the previous HTML4 version. Instead, it was designed from the beginning to be compatible with the previous standards, and to introduce some new technologies and new specifications developed by the latest WEB. into the new version of the standard.

2. HTML5 new features

2.1 Add new tags with specific meanings

Now basically all sites It is a div+css layout. Almost all article titles, content, auxiliary introductions, etc. are carried by div containers. When search engines crawl page content, because there is no clear meaning of containers, they can only guess whether these tag containers carry article titles or article content, etc. The new HTML5 standard directly adds HTML tags with specific meanings such as: <article>, <footer>, <header>, <nav>, <section>

2.2 New Add more intelligent form types

Previous form tags were just simple type constraints, such as text boxes, text fields, drop-down lists, etc. Controls such as form tag data verification that are closely integrated with the business are not well supported. They are basically used in conjunction with third-party JS controls. However, these third parties always involve version control, browser compatibility, Non-standard and a series of other issues. Smart forms are added directly to the HTML5 standard, making everything so simple, such as calendar, date, time, email, url, search

2.3 Make Web programs more independent and reduce dependence on third-party plug-ins.

In the HTML5 standard, audio, video, canvas and other technologies are natively supported. Make WEB programs more independent and better adapt to various forms of clients.

2.4 Better support for local offline storage

HTML5 provides two new methods for storing data on the client side:

localStorage - Data storage without time limit

sessionStorage - Data storage for a session

2.5 HTML5 real-time two-dimensional drawing, the introduction of canvas

The canvas element of HTML5 uses JavaScript to draw images on the web page. And has multiple ways to draw paths, rectangles, circles, characters, and add images.

2.6 JS supports multi-threading

The front end can perform large-scale operations without affecting UI update and browser-user interaction. Multi-threading can only be simulated through setTimeout and the like. In the new standard, the new HTML5 Web Worker object in JS natively supports multi-threading.

2.7 WebSockets makes cross-domain requests, long connections, and data push simple

WebSockets performs two-way communication on a (TCP) interface technology, PUSH technology type. WebSocket is a newly introduced function in the HTML5 specification. It is used to solve the problem of two-way communication between the browser and the backend server. Using WebSocket technology, the backend can push messages to the front end at any time to ensure the unified state of the front and backend. In the traditional stateless HTTP protocol, This is "cannot be done".

2.8 Better exception handling

HTML5 (text/html) browser will be more flexible in handling error syntax. HTML5 is designed so that older browsers can safely ignore new HTML5 code. Compared with HTML4.01, HTML5 provides complete rules for parsing, allowing different browsers to return exactly the same results even when syntax errors occur.

2.9 File API makes file uploading and file manipulation so easy

Because in projects, we often encounter the need to control local operations in web applications files, but in the past, some rich client technologies such as flash, ActiveX, Silverlight and other technologies were used. The newly provided HTML5 File API in HTML5 allows JS to be easily used.

In the follow-up, we will lead you to have a deeper understanding of HTML5