Ajax search

Posted under » JavaScript on 22 Aug 2019

In Drupal or google. When you search for something, it will suggest the pages you want to visit using Ajax.

Ajax uses XML HttpRequest or XHR in short.

You can use XML to store the list data like this (source). btw., the search function on top is done using this method.

<html>
<head>
<script>
function showResult(str) {
  if (str.length==0) {
    document.getElementById("livesearch").innerHTML="";
    document.getElementById("livesearch").style.border="0px";
    return;
  }
  var xmlhttp=new XMLHttpRequest();
  xmlhttp.onreadystatechange=function() {
    if (this.readyState==4 && this.status==200) {
      document.getElementById("livesearch").innerHTML=this.responseText;
      document.getElementById("livesearch").style.border="1px solid #A5ACB2";
    }
  }
  xmlhttp.open("GET","livesearch.php?q="+str,true);
  xmlhttp.send();
}
</script>
</head>
<body>

<form>
<input type="text" size="30" onkeyup="showResult(this.value)">
<div id="livesearch"></div>
</form>

</body>
</html>

Source code explanation: If the input field is empty (str.length==0), the function clears the content of the livesearch placeholder and exits the function.

If the input field is not empty, the showResult() function executes the following:

Create an XMLHttpRequest object or XHR
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 input field)

*There are 4 ready states on AJAX. readyState=4: This state is the symbol of the completion of the request. We can access the complete data that we requested and use it further to perform other operations or make some changes on the screen

The page on the server called by the JavaScript above is a PHP file called "livesearch.php".

The source code in "livesearch.php" searches an XML file for titles matching the search string and returns the result:

<¿php
$xmlDoc=new DOMDocument();
$xmlDoc->load("links.xml");

$x=$xmlDoc->getElementsByTagName('link');

//get the q parameter from URL
$q=$_GET["q"];

//lookup all links from the xml file if length of q>0
if (strlen($q)>0) {
  $hint="";
  for($i=0; $i<($x->length); $i++) {
    $y=$x->item($i)->getElementsByTagName('title');
    $z=$x->item($i)->getElementsByTagName('url');
    if ($y->item(0)->nodeType==1) {
      //find a link matching the search text
      if (stristr($y->item(0)->childNodes->item(0)->nodeValue,$q)) {
        if ($hint=="") {
          $hint="<a href='" .
          $z->item(0)->childNodes->item(0)->nodeValue .
          "' target='_blank'>" .
          $y->item(0)->childNodes->item(0)->nodeValue . "";
        } else {
          $hint=$hint . "<br /><a href='" .
          $z->item(0)->childNodes->item(0)->nodeValue .
          "' target='_blank'>" .
          $y->item(0)->childNodes->item(0)->nodeValue . "";
        }
      }
    }
  }
}

// Set output to "no suggestion" if no hint was found
// or to the correct values
if ($hint=="") {
  $response="no suggestion";
} else {
  $response=$hint;
}

//output the response
echo $response;
?>

If there is any text sent from the JavaScript (strlen($q) > 0), the following happens:

Load an XML file into a new XML DOM object
Loop through all <title> elements to find matches from the text sent from the JavaScript
Sets the correct url and title in the "$response" variable. If more than one match is found, all matches are added to the variable
If no matches are found, the $response variable is set to "no suggestion"