1 / 25

AJAX

AJAX. Introduction . All material from www.w3schools.com AJAX – what is it? Traditional web pages and operation Examples of AJAX use Creating an AJAX app AJAX workshop. AJAX – the basics. AJAX stands for Asynchronous JavaScript And XML Based on JavaScript and HTTP requests

saskia
Télécharger la présentation

AJAX

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. AJAX AJAX

  2. Introduction • All material from www.w3schools.com • AJAX – what is it? • Traditional web pages and operation • Examples of AJAX use • Creating an AJAX app • AJAX workshop AJAX

  3. AJAX – the basics • AJAX stands for Asynchronous JavaScript And XML • Based on JavaScript and HTTP requests • AJAX is a type of programming made popular in 2005 by Google (with Google Suggest) • AJAX is not a new programming language, but a new way to use existing standards • AJAX is good for creating better, faster, and more user-friendly web applications AJAX

  4. Prerequisites • HTML / XHTML • JavaScript • Knowledge of XML and CSS useful too AJAX

  5. How AJAX works • With AJAX, your JavaScript can communicate directly with the server, using the JavaScript XMLHttpRequest object. With this object, your JavaScript can trade data with a web server, without reloading the page • AJAX uses asynchronous data transfer (HTTP requests) between the browser and the web server, allowing web pages to request small bits of information from the server instead of whole pages. • The AJAX technique makes Internet applications smaller, faster and more user-friendly. • AJAX is a browser technology independent of web server software AJAX

  6. ‘Old’ way of getting/ sending data • In traditional JavaScript coding, to fetch or send information to or from a database or a file on webserver requires making an HTML form and GET or POST data to the server • User clicks "Submit" button to send/get the information, waits for the server to respond, then a complete new page loads with results • Since server returns a new page each time user submits input, traditional web apps can run slowly and tend to be less user-friendly AJAX

  7. AJAX Uses HTTP Requests • AJAX means JavaScript communicates directly with server, using JavaScript XMLHttpRequest object • With an HTTP request, web page can make a request to, and get a response from a web server - without reloading the entire page • The user remains on same page • Does not notice that scripts request pages, or send data to a server in the background • Greater transparency – better user experience AJAX

  8. The XMLHttpRequest Object • By using the XMLHttpRequest object, a web developer can update a page with data from the server after the page has loaded • AJAX was made popular in 2005 by Google (with Google Suggest). • Google Suggest uses the XMLHttpRequest object to create a very dynamic web interface: When you start typing in Google's search box, a JavaScript sends the letters off to a server and the server returns a list of suggestions • The XMLHttpRequest object is supported in Internet Explorer 5.0+, Safari 1.2, Mozilla 1.0 / Firefox, Opera 8+, and Netscape 7. AJAX

  9. Your First AJAX Application • To understand how AJAX works, we will create a small AJAX application • First, we are going to create a standard HTML form with two text fields: username and time • The username field will be filled in by the user and the time field will be filled in using AJAX. • The HTML file will be named "testAjax.htm • See next slide AJAX

  10. HTML form below has no submit button <html> <body> <form name="myForm"> Name: <input type="text" name="username" /> Time: <input type="text" name="time" /> </form> </body> </html> AJAX

  11. AJAX - Browser Support • The keystone of AJAX is the XMLHttpRequest object • Different browsers use different methods to create the XMLHttpRequest object • We don’t know which browser any user may use • Internet Explorer uses an ActiveXObject, while other browsers uses the built-in JavaScript object called XMLHttpRequest • To create this object, and deal with different browsers, we are going to use a "try and catch" statement AJAX

  12. <script type="text/javascript">function ajaxFunction() {var xmlHttp; try { // Firefox, Opera 8.0+, Safari xmlHttp=new XMLHttpRequest(); } catch (e) { // Internet Explorer try { xmlHttp=new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { xmlHttp=new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) {alert("Your browser does not support AJAX!");return false; } } }}</script> Script creates variable Comments IE can use 2 types of ActiveXObjects Warning for user if all browsers fail

  13. Code needed to make AJAX run • Tries to create the XMLHttpRequest object • Check non-IE browsers first • If the test fails, code first tries newer then older IE versions • Returns error message for very old browsers • Can be cut and paste into your AJAX page AJAX

  14. The XMLHttpRequest object • Has 3 important properties • onreadystatechange • readyState • responseText • The onreadystatechange property stores the function that will process the response from a server AJAX

  15. readyState • The readyState property holds the status of the server's response. We can use this to execute the onreadystatechange function • Possible values for the readyState property: • 0 The request is not initialized • 1 The request has been set up • 2 The request has been sent • 3 The request is in process • 4 The request is complete AJAX

  16. responseText • The data sent back from the server can be retrieved with the responseText property. • In our code, we will set the value of our "time" input field equal to responseText AJAX

  17. Here we test the server for response xmlHttp.onreadystatechange=function() { if(xmlHttp.readyState==4) { document.myForm.time.value=xmlHttp.responseText; } } AJAX

  18. Sending a request to a server • To send off a request to the server, we use the open() method and the send() method • The open() method takes three arguments • The first argument defines which method to use when sending the request (GET or POST) • The second argument specifies the URL of the server-side script • The third argument specifies that the request should be handled asynchronously (true or false) • The send() method sends the request off to the server AJAX

  19. When to send the request • We want to do this when the user releases a key after typing their name <form name="myForm"> Name: <input type="text" onkeyup="ajaxFunction();" name="username" /> Time: <input type="text" name="time" /> </form> Calls our function after key released AJAX

  20. Forming a changing server-side file • We will fetch the time from our server • Use php to deal with time request • Simple server-side file AJAX

  21. Fetching the time • We fetch time from a remote server’s php • ajaxtest.php • Place that in the code • Save the file as html • Place on your web server in same directory as php file • Bingo – page works (only with IE just now) AJAX

  22. alert("Your browser does not support AJAX!"); return false; } } } xmlHttp.onreadystatechange=function() { if(xmlHttp.readyState==4) { document.myForm.time.value=xmlHttp.responseText; } } xmlHttp.open("GET","ajaxtest.php",true); xmlHttp.send(null); } </script> <form name="myForm"> Name: <input type="text" onkeyup="ajaxFunction();" name="username" /> Time: <input type="text" name="time" /> </form> </body> </html> <html> <body> <script type="text/javascript"> function ajaxFunction() { var xmlHttp; try { // Firefox, Opera 8.0+, Safari xmlHttp=new XMLHttpRequest(); } catch (e) { // Internet Explorer try { xmlHttp=new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { xmlHttp=new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) {

  23. See our AJAX in action • http://engweb.info/ajax/ajaxtest.html • Works well in Mozilla • IE is a bit sketchy AJAX

  24. Conclusion • AJAX extends the usefulness of web apps • Saves entire pages reloading • Gives greater transparency to users • Data loads ‘in the background’ • Uses existing technologies • Is becoming very popular AJAX

  25. References • http://www.w3schools.com/ajax/default.asp • http://www.internetnews.com/dev-news/article.php/3676226 • http://daniel.lorch.cc/docs/ajax_simple/ AJAX

More Related