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Introduction to ajax
The document provides an introduction to AJAX (Asynchronous JavaScript and XML), detailing its definition, functionalities, and the advantages and disadvantages of using AJAX for web applications. It covers how to make AJAX requests using both raw JavaScript and jQuery, including various methods, usage samples, and debugging techniques. Additionally, it discusses AJAX in the context of ASP.NET and highlights security considerations for both server-side and client-side implementations.
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Introduction to ajax
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- 2. IntroductiontoAJAX Nir Elbaz Introduction to AJAX •Index • What is AJAX? • MakingAJAX requests with raw JavaScript • MakingAJAX requests with jQuery • AJAX & ASP.net • AJAX security
- 3. IntroductiontoAJAX Nir Elbaz What is AJAX •AJAX stands for Asynchronous JavaScript And XML • Allows web pages or parts of them to be updated asynchronously • Based on XML HTTP request object (AKA XHR) • Requires basic understanding of: • (X)HTML – displaying the data • CSS – styling the data • JavaScript – manipulating the DOM • XML / JSON – received / sent data format (also HTML & text) Also refers dynamic content
- 4. IntroductiontoAJAX Nir Elbaz What is AJAX Browser UserInterface Web Server Databases, backend processes HTTP(S)Transport HTTP request HTML/CSS/JS/* response Classic web application model Browser User Interface Web Server Databases, backend processes HTTP(S)Transport HTTP request HTML/CSS/JS/* response AJAX web application model AJAX engine JS call Validresponsecanbeanytextualdata:html,css,js,csv,xml…
- 5. IntroductiontoAJAX Nir Elbaz What is AJAX Classicweb application model AJAX web application model User Front end Back end
- 6. IntroductiontoAJAX Nir Elbaz What is AJAX •Usage samples • Autocomplete search textboxes (sample) • Cascading dropdown list boxes (sample) • Real-time - Continuous data refresh (long polling, chat systems…) • Immediate forms validation feedback (sample) • Conditional display / dynamic content (sample) • Auto save user information (Google Docs, Facebook) • Ratings, voting & other instant actions (sample)
- 7. IntroductiontoAJAX Nir Elbaz What is AJAX •Browser support • Mozilla Firefox 1.0 and above • Google Chrome • Apple Safari 1.2 and above • Microsoft Internet Exporer 5 and above (ActiveXObject for lte IE6) • Opera 7.6 and above
- 8. IntroductiontoAJAX Nir Elbaz What is AJAX •Pros • Better interactivity & responsiveness • Impressive UX • Reduced connections to the web server (partial rendering) • Reduced bandwidth • Its “cool”
- 9. IntroductiontoAJAX Nir Elbaz What is AJAX •Cons • The back and refresh button are rendered useless • Bookmarking is useless (HTML 5 History API to the rescue) • Requires JavaScript to be enabled on browsers • SEO & analytics unfriendly • Screen readers unfriendly – affects accessibility • Callbacks can lead to complex code • Network latency may break usability
- 10. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith raw JavaScript • Basic steps • A client event occurs (button click, setTimeout fired…) • An XMLHttpRequest object is created • The XMLHttpRequest object is configured • The XMLHttpRequest object makes an asynchronous request to theWebserver • Webserver returns the result • The XMLHttpRequest object calls the callback() function and processes the result
- 11. IntroductiontoAJAX Nir Elbaz MakingAJAXrequestswithrawJavaScript readyState codes: 0: objectcreated but uninitialized 1: loading (opened, not sent) 2: loaded (send but no response) 3: interactive (partial response) 4: complete (full response) status (HTTP) codes: 1xx: (Provisional response) 2xx: (Successful) 3xx: (Redirected) 4xx: (Request error) 5xx: (Server error) Samples: 200 - the server successfully returned the page 404 - the requested page doesn't exist 503 - the server is temporarily unavailable Methods: open(method, url, async) send(string) setRequestHeader(header, value)
- 12. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith raw JavaScript • GET or POST? • GET is faster and simpler than POST • Use POST in these cases: • A cached file is not an option (update a file or database on the server) • Sending a large amount of data to the server (POST has no size limitations) • Sending user input (which can contain unknown characters)
- 13. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith raw JavaScript • Usage samples GET request (-params, +cache) xmlhttp.open(“GET”, “myWS.asp”, true); xmlhttp.send(“”); GET request (-params, -cache) xmlhttp.open(“GET”, “myWS.asp?t=” + Math.random(), true); xmlhttp.send(“”); GET request (+params, +cache) xmlhttp.open(“GET”, “myWS.asp?fname=Nir&lname=Elbaz”, true); xmlhttp.send(“”); POST request (+params, -cache) xmlhttp.open(“POST”, “myWS.asp”, true); xmlhttp.send(“fname=Nir&lname=Elbaz”); // sending params now
- 14. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith raw JavaScript • Callback sample • Can get either free text (e.g. HTML, JS…) or XML document • Can get response header value with getResponseHeader(‘HEADER’)
- 15. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith raw JavaScript • Debugging XHR • DeveloperTools (Chrome, FireBug….) • Fiddler • … XHR requests logs in Chrome DeveloperTools
- 16. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith jQuery • jQuery provides great support forAJAX & simplify usage: • load(url, data, callback): Load a piece of html into a container DOM • $.getJSON(url, data, callback): Load a JSON with GET method • $.getScript(url, callback): Load a JavaScript • $.get(url, data, callback, type):GenericAJAX GET request • $.post(url, data, callback, type): Generic AJAX GET request • $.ajax(options):All purpose AJAX request (higher level abstractions) Syntacticsugarof$.ajax GET, POST GET GET POST GET, POST
- 17. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith jQuery • Usage samples Load (part of a) remote file $("#result").load(loadUrl); $("#result").load(loadUrl + " #picture"); // Best practice: Use HTML(‘<img src=“loader.gif” />’) before calling the load function Load remote file w/ parameters $("#result").load(loadUrl, “fname=Nir&lname=Elbaz”); // GET $("#result").load(loadUrl, {fname:“Nir”, lname:“Elbaz”}); // POST // Best practice: Use HTML(‘<img src=“loader.gif” />’) before calling the load function
- 18. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith jQuery • Usage samples Get JSON file (GET only), generate HTML fragment and append to HTML $.getJSON(“http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=?”, { tags: “Israel”, tagmode: “any”, format: “json” }) .done(function (data) { $.each(data.items, function(index, item ) { $(“<img/>”).attr(“src”, item.media.m).appendTo(“#images”); }); }); JSONP
- 19. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith jQuery • Usage samples Full documentation of the $.ajax method Send id as data to the server and notify the user once it’s complete or fail $.ajax({ url: “someWS.ashx”, type: “POST”, data: {id : 3}, dataType: "html" }).done(function (msg) { $("#log").html(msg); }).fail(function (jqXHR, textStatus) { alert("Request failed: " + textStatus); });
- 20. IntroductiontoAJAX Nir Elbaz Making AJAX requestswith jQuery • More jQueryAJAX aid methods • $.ajaxSetup(): Sets the default values for future AJAX requests • $.param():Creates a serialized representation of an array or object • ajaxStart(): Specifies a function to run when the first AJAX request begins • ajaxError(): Specifies a function to run when AJAX request completes with an error • serialize(): Encodes a set of form elements as a string for submission • …
- 21. IntroductiontoAJAX Nir Elbaz AJAX & ASP.net •Formerly known as projectATLAS • Released on 2007 as part of ASP.net v.2 • AJAX is even more crucial onASP.net web applications (LC,ViewState…) • Provides few server side controls to simplify AJAX development but considered insufficient
- 22. IntroductiontoAJAX Nir Elbaz AJAX & ASP.net •AJAX built-in server side controls • ScriptManager - Manages script resources for client components • UpdatePanel * - enables you to refresh selected parts of the page • UpdateProgress * - Provides status information about partial-page updates in UpdatePanel controls • Timer * - Performs postbacks at defined intervals (w or w/o UpdatePanel) • AJAX ControlsToolkit • Set of additional server controls which provide highly responsive and interactiveAjax- enabledWeb applications (link) * ScriptManager control is required in order to use the UpdatePanel, UpdateProgress, andTimer controls
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- 25. IntroductiontoAJAX Nir Elbaz AJAX Security • Serverside: • Same as regular web applications in all aspects • Client side: • JS code is visible to a user/hacker, which can use it to search for exploits
- 26. IntroductiontoAJAX Nir Elbaz BehindThe Scenes (Ina Nutshell) • A web service is any piece of SW that makes itself available over the internet • Could be based on various technologies server pages (php, asp|m|hx, sc…) asmx ashx wcf
- 27. IntroductiontoAJAX Nir Elbaz Resources • http://www.w3schools.com/ajax/ • http://www.tutorialspoint.com/ajax/ •http://en.wikipedia.org/wiki/Ajax_(programming) • http://net.tutsplus.com/ • http://www.w3schools.com/jquery/jquery_ref_ajax.asp • http://api.jquery.com/jQuery.ajax/ • http://msdn.microsoft.com/en-us/library/bb398874(v=vs.100).aspx