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What is AJAX? AJAX is a developer's dream, because you can:
Read data from a web server - after a web page has loaded Update a web page without reloading the page Send data to a web server - in the background What is AJAX? AJAX = Asynchronous JavaScript And XML. AJAX is not a programming language. AJAX just uses a combination of: A browser built-in XMLHttpRequest object (to request data from a web server) JavaScript and HTML DOM (to display or use the data)
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The HTML page contains a <div> section and a <button>.
The <div> section is used to display information from a server. The <button> calls a function (if it is clicked). The function requests data from a web server and displays it:
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loadDoc()
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Code Example <script> function loadDoc() {
<!DOCTYPE html> <html> <body> <div id="demo"> <h2>The XMLHttpRequest Object</h2> <button type="button" onclick="loadDoc()">Change Content</button> </div> <script> function loadDoc() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { document.getElementById("demo").innerHTML = this.responseText; } }; xhttp.open("GET", "ajax_info.txt", true); xhttp.send(); </script> </body> </html>
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How Ajax Work?
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The XMLHttpRequest Object
All modern browsers support the XMLHttpRequest object. The XMLHttpRequest object can be used to exchange data with a web server behind the scenes. This means that it is possible to update parts of a web page, without reloading the whole page.
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Create an XMLHttpRequest Object
All modern browsers (Chrome, Firefox, IE7+, Edge, Safari, Opera) have a built-in XMLHttpRequest object. Syntax for creating an XMLHttpRequest object:
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GET or POST? GET is simpler and faster than POST, and can be used in most cases. However, always use POST requests when: 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), POST is more robust and secure than GET. GET Requests
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AJAX PHP <!DOCTYPE html> <html> <body>
<h2>The XMLHttpRequest Object</h2> <h3>Start typing a name in the input field below:</h3> <p>Suggestions: <span id="txtHint"></span></p> <p>First name: <input type="text" id="txt1" onkeyup="showHint(this.value)"></p> <script> function showHint(str) { var xhttp; if (str.length == 0) { document.getElementById("txtHint").innerHTML = ""; return; } xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { document.getElementById("txtHint").innerHTML = this.responseText; }; xhttp.open("GET", "gethint.php?q="+str, true); xhttp.send(); </script> </body> </html> AJAX PHP
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gethint.php The PHP File - "gethint.php”
<?php // Array with names $a[] = "Anna"; $a[] = "Brittany"; $a[] = "Cinderella"; $a[] = "Diana"; $a[] = "Eva"; $a[] = "Fiona"; $a[] = "Gunda"; $a[] = "Hege"; $a[] = "Inga"; $a[] = "Johanna"; $a[] = "Kitty"; $a[] = "Linda"; $a[] = "Nina"; $a[] = "Ophelia"; $a[] = "Petunia"; $a[] = "Amanda"; $a[] = "Raquel"; $a[] = "Cindy"; $a[] = "Doris"; $a[] = "Eve"; $a[] = "Evita"; $a[] = "Sunniva"; $a[] = "Tove"; $a[] = "Unni"; $a[] = "Violet"; $a[] = "Liza"; $a[] = "Elizabeth"; $a[] = "Ellen"; $a[] = "Wenche"; $a[] = "Vicky"; // get the q parameter from URL $q = $_REQUEST["q"]; $hint = ""; // lookup all hints from array if $q is different from "" if ($q !== "") { $q = strtolower($q); $len=strlen($q); foreach($a as $name) { if (stristr($q, substr($name, 0, $len))) { if ($hint === "") { $hint = $name; } else { $hint .= ", $name"; } } } } // Output "no suggestion" if no hint was found or output correct values echo $hint === "" ? "no suggestion" : $hint; ?> gethint.php The PHP File - "gethint.php” The PHP file checks an array of names, and returns the corresponding name(s) to the browser:
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AJAX Database
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The showCustomer() function does the following:
Check if a customer is selected Create an XMLHttpRequest object Create the function to be executed when the server response is ready Send the request off to a file on the server Notice that a parameter (q) is added to the URL (with the content of the dropdown list)
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The AJAX Server Page <?php $mysqli = new mysqli("servername", "username", "password", "dbname"); if($mysqli->connect_error) { exit('Could not connect'); } $sql = "SELECT customerid, companyname, contactname, address, city, postalcode, country FROM customers WHERE customerid = ?"; $stmt = $mysqli->prepare($sql); $stmt->bind_param("s", $_GET['q']); $stmt->execute(); $stmt->store_result(); $stmt->bind_result($cid, $cname, $name, $adr, $city, $pcode, $country); $stmt->fetch(); $stmt->close(); echo "<table>"; echo "<tr>"; echo "<th>CustomerID</th>"; echo "<td>" . $cid . "</td>"; echo "<th>CompanyName</th>"; echo "<td>" . $cname . "</td>"; echo "<th>ContactName</th>"; echo "<td>" . $name . "</td>"; echo "<th>Address</th>"; echo "<td>" . $adr . "</td>"; echo "<th>City</th>"; echo "<td>" . $city . "</td>"; echo "<th>PostalCode</th>"; echo "<td>" . $pcode . "</td>"; echo "<th>Country</th>"; echo "<td>" . $country . "</td>"; echo "</tr>"; echo "</table>"; ?> The page on the server called by the JavaScript above is a PHP file called "getcustomer.php". The source code in "getcustomer.php" runs a query against a database, and returns the result in an HTML table:
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<html> <head> <style> table, th, td { border: 1px solid black; border-collapse: collapse; } th, td { padding: 5px; } </style> </head> <body> <table id="demo"></table> <script> function loadXMLDoc() { var xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { myFunction(this); } }; xmlhttp.open("GET", "cd_catalog.xml", true); xmlhttp.send(); } function myFunction(xml) { var i; var xmlDoc = xml.responseXML; var table="<tr><th>Artist</th><th>Title</th></tr>"; var x = xmlDoc.getElementsByTagName("CD"); for (i = 0; i <x.length; i++) { table += "<tr><td>" + x[i].getElementsByTagName("ARTIST")[0].childNodes[0].nodeValue + "</td><td>" + x[i].getElementsByTagName("TITLE")[0].childNodes[0].nodeValue + "</td></tr>"; } document.getElementById("demo").innerHTML = table; } </script> </body> </html> AJAX and XML
![<html> <head> <style> table, th, td { border: 1px solid black; border-collapse: collapse; } th, td { padding: 5px; } </style> </head> <body> <table id= demo ></table> <script> function loadXMLDoc() { var xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { myFunction(this); } }; xmlhttp.open( GET , cd_catalog.xml , true); xmlhttp.send(); } function myFunction(xml) { var i; var xmlDoc = xml.responseXML; var table= <tr><th>Artist</th><th>Title</th></tr> ; var x = xmlDoc.getElementsByTagName( CD ); for (i = 0; i <x.length; i++) { table += <tr><td> + x[i].getElementsByTagName( ARTIST )[0].childNodes[0].nodeValue + </td><td> + x[i].getElementsByTagName( TITLE )[0].childNodes[0].nodeValue + </td></tr> ; } document.getElementById( demo ).innerHTML = table; } </script> </body> </html>](http://slideplayer.com./slide/17217281/99/images/18/%3Chtml%3E+%3Chead%3E+%3Cstyle%3E+table%2C+th%2C+td+%7B+border%3A+1px+solid+black%3B+border-collapse%3A+collapse%3B+%7D+th%2C+td+%7B+padding%3A+5px%3B+%7D+%3C%2Fstyle%3E+%3C%2Fhead%3E+%3Cbody%3E+%3Ctable+id%3D+demo+%3E%3C%2Ftable%3E+%3Cscript%3E+function+loadXMLDoc%28%29+%7B+var+xmlhttp+%3D+new+XMLHttpRequest%28%29%3B+xmlhttp.onreadystatechange+%3D+function%28%29+%7B+if+%28this.readyState+%3D%3D+4+%26%26+this.status+%3D%3D+200%29+%7B+myFunction%28this%29%3B+%7D+%7D%3B+xmlhttp.open%28+GET+%2C+cd_catalog.xml+%2C+true%29%3B+xmlhttp.send%28%29%3B+%7D+function+myFunction%28xml%29+%7B+var+i%3B+var+xmlDoc+%3D+xml.responseXML%3B+var+table%3D+%3Ctr%3E%3Cth%3EArtist%3C%2Fth%3E%3Cth%3ETitle%3C%2Fth%3E%3C%2Ftr%3E+%3B+var+x+%3D+xmlDoc.getElementsByTagName%28+CD+%29%3B+for+%28i+%3D+0%3B+i+%3Cx.length%3B+i%2B%2B%29+%7B+table+%2B%3D+%3Ctr%3E%3Ctd%3E+%2B+x%5Bi%5D.getElementsByTagName%28+ARTIST+%29%5B0%5D.childNodes%5B0%5D.nodeValue+%2B+%3C%2Ftd%3E%3Ctd%3E+%2B+x%5Bi%5D.getElementsByTagName%28+TITLE+%29%5B0%5D.childNodes%5B0%5D.nodeValue+%2B+%3C%2Ftd%3E%3C%2Ftr%3E+%3B+%7D+document.getElementById%28+demo+%29.innerHTML+%3D+table%3B+%7D+%3C%2Fscript%3E+%3C%2Fbody%3E+%3C%2Fhtml%3E.jpg "AJAX and XML.")
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AJAX and XML Display the First CD in an HTML div Element
<!DOCTYPE html> <html> <body> <div id='showCD'></div> <script> displayCD(0); function displayCD(i) { var xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { myFunction(this, i); } }; xmlhttp.open("GET", "cd_catalog.xml", true); xmlhttp.send(); function myFunction(xml, i) { var xmlDoc = xml.responseXML; x = xmlDoc.getElementsByTagName("CD"); document.getElementById("showCD").innerHTML = "Artist: " + x[i].getElementsByTagName("ARTIST")[0].childNodes[0].nodeValue + "<br>Title: " + x[i].getElementsByTagName("TITLE")[0].childNodes[0].nodeValue + "<br>Year: " + x[i].getElementsByTagName("YEAR")[0].childNodes[0].nodeValue; </script> </body> </html> AJAX and XML
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AJAX and XML Navigate Between the CDs Page 1 <!DOCTYPE html>
<body> <div id='showCD'></div><br> <input type="button" onclick="previous()" value="<<"> <input type="button" onclick="next()" value=">>"> <script> var i = 0, len; displayCD(i); function displayCD(i) { var xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { myFunction(this, i); } }; xmlhttp.open("GET", "cd_catalog.xml", true); xmlhttp.send(); AJAX and XML
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AJAX and XML Navigate Between the CDs Page 2
function myFunction(xml, i) { var xmlDoc = xml.responseXML; x = xmlDoc.getElementsByTagName("CD"); len = x.length; document.getElementById("showCD").innerHTML = "Artist: " + x[i].getElementsByTagName("ARTIST")[0].childNodes[0].nodeValue + "<br>Title: " + x[i].getElementsByTagName("TITLE")[0].childNodes[0].nodeValue + "<br>Year: " + x[i].getElementsByTagName("YEAR")[0].childNodes[0].nodeValue; } function next() { if (i < len-1) { i++; displayCD(i); function previous() { if (i > 0) { i--; </script> </body> </html> AJAX and XML
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