Essentials of Javascript - Cultural View

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Ajax (programming) 49 Since then, however, there have been a number of developments in the technologies used in an Ajax application, and the definition of the term Ajax. In particular, it has been noted that: • JavaScript is not the only client-side scripting language that can be used for implementing an Ajax application. Other languages such as VBScript are also capable of the required functionality. [2] [9] However JavaScript is the most popular language for Ajax programming due to its inclusion in and compatibility with the majority of modern web browsers. • XML is not required for data interchange and therefore XSLT is not required for the manipulation of data. JavaScript Object Notation (JSON) is often used as an alternative format for data interchange, [10] although other formats such as preformatted HTML or plain text can also be used. [11] Classic Ajax involves writing ad hoc JavaScript on the client. A simpler if cruder alternative is to use standard JavaScript libraries that can partially update a page, such as ASP.Net's UpdatePanel. Tools such as Echo2 and ZK enable fine grained control of a page from the server, using only standard JavaScript libraries. Introducing XMLHttpRequest and pseudomultithreading, it is possible to swap the role of client and server (web browser may start behaving as a server and web server may start behaving as a client) in Client-Server model. Drawbacks • Owing to their dynamic nature, Ajax interfaces are often harder to develop when compared to static pages. • Pages dynamically created using successive Ajax requests do not automatically register themselves with the browser's history engine, so clicking the browser's "back" button may not return the user to an earlier state of the Ajax-enabled page, but may instead return them to the last full page visited before it. Workarounds include the use of invisible IFrames to trigger changes in the browser's history and changing the URL fragment identifier (the [12] [13] portion of a URL after the '#') when Ajax is run and monitoring it for changes. • Dynamic web page updates also make it difficult for a user to bookmark a particular state of the application. Solutions to this problem exist, many of which use the URL fragment identifier (the portion of a URL after the '#') [12] [13] to keep track of, and allow users to return to, the application in a given state. • Depending on the nature of the Ajax application, dynamic page updates may interfere disruptively with user interactions, especially if working on an unstable internet connection. For instance, editing a search field may trigger a query to the server for search completions, but the user may not know that a search completion popup is forthcoming, and if the internet connection is slow, the popup list may show up at an inconvenient time, when the user has already proceeded to do something else. • Because most web crawlers do not execute JavaScript code, [14] publicly indexable web applications should provide an alternative means of accessing the content that would normally be retrieved with Ajax, to allow search engines to index it. • Any user whose browser does not support JavaScript or XMLHttpRequest, or simply has this functionality disabled, will not be able to properly use pages which depend on Ajax. Similarly, devices such as mobile phones, PDAs, and screen readers may not have support for the required technologies. Screen readers that are able to use Ajax may still not be able to properly read the dynamically generated content. [15] The only way to let the user carry out functionality is to fall back to non-JavaScript methods. This can be achieved by making sure links and forms can be resolved properly and do not rely solely on Ajax. In JavaScript, form submission could then be halted with "return false". [16] • The same origin policy prevents some Ajax techniques from being used across domains, [7] although the W3C has a draft of the XMLHttpRequest object that would enable this functionality. [17] Techniques exist to sidestep this limitation by using a special Cross Domain Communications channel embedded as an iframe within a page. [18] • Like other web technologies, Ajax has its own set of vulnerabilities that developers must address. Developers familiar with other web technologies may have to learn new testing and coding methods to write secure Ajax [19] [20] applications.
Ajax (programming) 50 • Ajax-powered interfaces may dramatically increase the number of user-generated requests to web servers and their back-ends (databases, or other). This can lead to longer response times and/or additional hardware needs. See also • Ajax framework • ASP.NET AJAX • Comet (programming) • Reverse Ajax • Rich Internet application • XMLHttpRequest • Google Web Toolkit • jQuery Framework (Ajax) External links • Ajax: A New Approach to Web Applications [21] Article that coined the term and Q&A. • Ajax (programming) [22] at the Open Directory Project • Ajax Tutorial [23] with get, post, text and XML examples. • Mastering Ajax Tutorial [24] . References [1] Jesse James Garrett (2005-02-18). "Ajax: A New Approach to Web Applications" (http://www.adaptivepath.com/ideas/essays/archives/ 000385.php). AdaptivePath.com. . Retrieved 2008-06-19. [2] Ullman, Chris (March 2007). Beginning Ajax (http://www.wrox.com/WileyCDA/Section/id-303217.html). wrox. ISBN 978-0-470-10675-4. . Retrieved 2008-06-24. [3] "Code Samples and Apps: Applets" (http://java.sun.com/applets/). Sun Microsystems, Inc.. . Retrieved 2009-01-02. [4] Hinchcliffe, Dion (June 2006). Real-World Ajax: Secrets of the Masters (http://ajaxdevelopersjournal.com/read/338113.htm). SYS-CON Media. ISBN 9780977762200. . [5] "Dynamic HTML and XML: The XMLHttpRequest Object" (http://developer.apple.com/internet/webcontent/xmlhttpreq.html). Apple Inc. . Retrieved 2008-06-25. [6] Hopmann, Alex. "Story of XMLHTTP" (http://www.alexhopmann.com/story-of-xmlhttp/). Alex Hopmann’s Blog. . Retrieved 17 May 2010. [7] "A Brief History of Ajax" (http://www.aaronsw.com/weblog/ajaxhistory). Aaron Swartz. 2005-12-22. . Retrieved 2009-08-04. [8] Gregory E. Aldridge (2003-03-09). "System and method for providing a browser-based user interface" (http://www.uspto.gov/web/ patents/patog/week16/OG/html/1341-3/US07523401-20090421.html). United States Patent and Trademark Office. . Retrieved 2010-03-28. [9] But use of VBScript assumes the target browser supports it. [10] "JSON - JavaScript Object Notation" (http://tapestry.apache.org/tapestry4.1/ajax/json.html). Apache.org. . Retrieved 2008-07-04. [11] "Speed Up Your Ajax-based Apps with JSON" (http://www.devx.com/webdev/Article/32651). DevX.com. . Retrieved 2008-07-04. [12] "Why use Ajax?" (http://www.interaktonline.com/support/articles/Details/Ajax:+Asynchronously+Moving+Forward-Why+use+ Ajax?.html?id_art=36&id_asc=309). InterAKT. 2005-11-10. . Retrieved 2008-06-26. [13] "Deep Linking for AJAX" (http://blog.onthewings.net/2009/04/08/deep-linking-for-ajax/). . [14] Prokoph, Andreas (2007-05-08). "Help Web crawlers efficiently crawl your portal sites and Web sites" (http://www.ibm.com/ developerworks/library/x-sitemaps/index.html). IBM. . Retrieved 2009-04-22. [15] Edwards, James (2006-05-05). "Ajax and Screenreaders: When Can it Work?" (http://www.sitepoint.com/article/ ajax-screenreaders-work). sitepoint.com. . Retrieved 2008-06-27. [16] Quinsey, Peter. "User-Proofing Ajax" (http://www.alistapart.com/articles/userproofingajax). . [17] "Access Control for Cross-Site Requests" (http://dev.w3.org/2006/waf/access-control/). World Wide Web Consortium. . Retrieved 2008-06-27. [18] "Secure Cross-Domain Communication in the Browser" (http://msdn.microsoft.com/en-us/library/bb735305.aspx). The Architecture Journal (MSDN). . Retrieved 2010-04-27. [19] Sullivan, Bryan. "Testing for security in the age of Ajax Programming" (http://www.developerfusion.com/article/6197/ testing-for-security-in-the-age-of-ajax-programming/). developerFusion. . Retrieved 2008-10-15.
Page 1 and 2: Essentials of Javascript Visit the
Page 3 and 4: John Resig 122 Reverse Ajax 123 Ric
Page 5 and 6: JavaScript 2 History Anyway I know
Page 7 and 8: JavaScript 4 Prototype-based protot
Page 9 and 10: JavaScript 6 LCMCalculator.prototyp
Page 11 and 12: JavaScript 8 Example - use in web p
Page 13 and 14: JavaScript 10 request that might ha
Page 15 and 16: JavaScript 12 Application platform
Page 17 and 18: JavaScript 14 See also • Client-s
Page 19 and 20: JavaScript 16 [25] Robert Nyman, Ge
Page 21 and 22: JavaScript syntax 18 JavaScript syn
Page 23 and 24: JavaScript syntax 20 Primitive data
Page 25 and 26: JavaScript syntax 22 String A Strin
Page 27 and 28: JavaScript syntax 24 Native Objects
Page 29 and 30: JavaScript syntax 26 } Math The Mat
Page 31 and 32: JavaScript syntax 28 // ? - 0 or 1
Page 33 and 34: JavaScript syntax 30 Operators The
Page 35 and 36: JavaScript syntax 32 alert( Boolean
Page 37 and 38: JavaScript syntax 34 Conditional op
Page 39 and 40: JavaScript syntax 36 With The with
Page 41 and 42: JavaScript syntax 38 Methods A meth
Page 43 and 44: JavaScript syntax 40 Inheritance Ja
Page 45 and 46: JavaScript syntax 42 See also • C
Page 47 and 48: JavaScript Style Sheets 44 } fontSi
Page 49 and 50: JavaScript engine 46 JavaScript eng
Page 51: Ajax (programming) 48 Ajax (program
Page 55 and 56: ?: 52 ?: In computer programming, ?
Page 57 and 58: ?: 54 Furthermore, the ternary oper
Page 59 and 60: ?: 56 ?: in style guidelines Some c
Page 61 and 62: Appcelerator Titanium 58 See also
Page 63 and 64: Bookmarklet 60 Bookmarklet A bookma
Page 65 and 66: Bookmarklet 62 References [1] Domai
Page 67 and 68: Client-side JavaScript 64 implement
Page 69 and 70: Client-side JavaScript 66 Reference
Page 71 and 72: dhtmlx [1] Comparison of JavaScript
Page 73 and 74: ility / ion Comparison of JavaScrip
Page 75 and 76: Comparison of JavaScript frameworks
Page 77 and 78: Comparison of JavaScript frameworks
Page 79 and 80: Comparison of JavaScript-based sour
Page 81 and 82: Comparison of JavaScript-based sour
Page 83 and 84: Douglas Crockford 80 Douglas Crockf
Page 85 and 86: DWR (Java) 82 DWR (Java) Developer(
Page 87 and 88: EMVC 84 EMVC Developer(s) Ed Hertzo
Page 89 and 90: Brendan Eich 86 References [1] Stev
Page 91 and 92: JSDoc 88 JSDoc JSDoc is a syntax fo
Page 93 and 94: JSDoc 90 History The earliest examp
Page 95 and 96: JSSP 92 JSSP JSSP, or JavaScript Se
Page 97 and 98: JScript 94 JScript is sometimes ref
Page 99 and 100: JScript 96 [9] http://msdn2.microso
Page 101 and 102: JSON 98 JSON Filename extension .js
Page 103 and 104:
JSON 100 Using JSON in Ajax The fol
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JSON 102 /> state='NY' postalCode='
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JSON 104 parseResponse({"Name": "Ch
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JSON 106 [21] Ben-Kiki, Oren; Evans
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JsonML 108 ["person", {"created":"
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Lightbox (JavaScript) 110 Lightbox
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Lively Kernel 112 Lively Kernel Liv
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Lively Kernel 114 The Lively Wiki T
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Lively Kernel 116 }); } External li
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Minification (programming) 118 Mini
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Objective-J 120 Objective-J Paradig
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John Resig 122 John Resig John Resi
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Reverse Ajax 124 External links •
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Seed (programming) 126 Seed (progra
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Seed (programming) 128 See also •
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Comparison of Server-side JavaScrip
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SproutCore 136 • Tasks. Tasks man
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Unobtrusive JavaScript 138 }); Beca
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Venkman 140 External links • Venk
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XMLHttpRequest 142 Microsoft added
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XMLHttpRequest 144 The send method
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XMLHttpRequest 146 [21] "Specificat
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Article Sources and Contributors 14
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Article Sources and Contributors 15
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License 152 License Creative Common
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