Jquery Course

This tutorial shows you how to change the CSS file included into your page, using jQuery.
For example, if we have 2 CSS files, "style.css" and "style2.css", we can set a jQuery code to alternate the CSS included into our page, between these two files, when the user clicks on a specific element.


Here's an example, a simple web page with a <div> and a paragraph. When a user clicks on this DIV, a jQuery instruction changes /alternate the css file included into this page, in a <style> tag which has id="stl" (for details, see the comments in code).

The Web page

<!doctype html>
<html>
<head>
<meta charset="utf-8" />
<title>Change CSS file</title>
<link href="style.css" rel="stylesheet" type="text/css" id="stl" />
<script type="text/javascript" src="jquery_library.js"></script>
<script type="text/javascript"><!--
// the CSS file is chosen  according to the positive or negative value of this variable
var plusmin = 1;

$(document).ready(function() {
  // when click on the element with id="idd"
  $('#idd').click(function(){
    plusmin *= -1;        // change the polarity of "plusmin" var
    var stl = plusmin>0 ? 'style.css' : 'style2.css';     // sets the css file, according to plusmin

    // change the css file of the tag with id="stl" and rel="stylesheet"
    $('#stl[rel=stylesheet]').attr('href', stl);
  });
});
--></script>
</head>
<body>
<div id="idd"> Click here:<br />
Alternate the CSS file for this page<br />
Between "style.css" and "style2.css"</div>
<p class="hdp">This paragraph has display:none; in style2.css</p>
</body>
</html>

style.css file

body { text-align: center; }
#idd {
 width: 200px;
 background: #a7efa8;
 margin: 2px auto;
 border: 2px solid blue;
 padding: 5px 8px;
 text-align: left;
 font-size: 16px;
 cursor: pointer;
}

style2.css file

#idd {
 width: 300px;
 margin: 2px auto 2px 80px;
 background: #dadafe;
 border: 2px dashed #a0cea1;
 padding: 5px 8px;
 font-size: 16px;
 font-weight: bold;
 text-align: center;
 cursor: pointer;
}
p.hdp { display: none; }

Demo:
Click here:
Alternate the CSS file for this page
Between "style.css" and "style2.css"

This paragraph has display:none; in style2.css

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which tag is used in <table> to create table header cell?
<thead> <th> <td>
<table><tr>
  <th>Title 1</th>
  <th>Title 2</th>
</tr></table>
Which CSS property sets the distance between lines?
line-height word-spacing margin
.some_class {
  line-height: 150%;
}
Which function opens a new browser window.
alert() confirm() open()
document.getElementById("id_button").onclick = function(){
  window.open("http://coursesweb.net/");
}
Indicate the PHP function that returns an array with names of the files and folders inside a directory.
mkdir() scandir() readdir()
$ar_dir = scandir("dir_name");
var_export($ar_dir);
Change CSS file with jQuery

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