How can I change the css class rules using jQuery?

user_55860 0
Viewed 86081

Can any one help me please, I have two sections of my question.

  1. What I want to do is changing css class rules using jQuery on the fly.

    .classname{color:red; font-size:14px;}

    In example above I have a class named .classname now using jQuery I want to change the font size only not color with in .classname not by adding css inline.

  2. I want to create and save .classname change to a file remember there will be complete stylesheet or no of classnames that will be save in file.

How I can do this the easiest and better way?

Thanks!

css jquery
14 Answers

As far as I know there's no jQuery way to do this. There might be some jQuery plugin for this but I don't know.

Basically, what you're trying to achieve in your first question is possible using the styleSheets property of the document object. It's a little bit more complicated than that as you need to walk to a rather deep object chain, but nevertheless works in all major browsers including Internet Explorer 6. Below is a proof of concept. The CSS is inside a STYLE tag, but works with external CSS just as well. I'll let you do the abstractions.

Proof of Concept

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

<html>
<head>
<title></title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<meta http-equiv="imagetoolbar" content="false">
<meta http-equiv="imagetoolbar" content="no">
<style type="text/css">
.classname {
 color: red;
 font-size: 14px;
}
</style>
<script type="text/javascript">
window.onload = function() {
    document.getElementById("button").onclick = function() {
        var ss = document.styleSheets;

        for (var i=0; i<ss.length; i++) {
            var rules = ss[i].cssRules || ss[i].rules;

            for (var j=0; j<rules.length; j++) {
                if (rules[j].selectorText === ".classname") {
                    rules[j].style.color = "green";
                }
            }
        }
    };
}
</script>
</head>
<body>

<h1 class="classname">Some red text</h1>

<button id="button">Make text green</button>

</body>
</html>

For your second question, I don't have time to write a solution but it would involve reading the CSS declarations just as above and use the cssText property of a CssRule object in order to build a string which will eventually be sent to the server using a Ajax POST request. The server side is your business.

References:

Hope it helps

Ionut_G_Stan_588080

If I understand your question correctly, you would like to read through a CSS file, make changes to a class and then persist those changes by saving the file?

You can't do this with JavaScript/jQuery running from the client side; You can certainly change the font size of each individual element in the DOM that matches the CSS class .classname, like so

$('.classname').css('font-size','14px');

but client-side JavaScript cannot access the filesystem from the web browser, so you would need some other way (i.e. server-side code) to make changes to the CSS file itself.

Russ_Cam_18310

What you are looking to do is done by having a couple of themes on the server (theme1.css, theme2.css, theme3.css, etc.) and letting the user select the theme he likes. You can then save in the database with the user profile the theme the user chose (theme2.css). When the user then displays his page, you include at the top of the page the theme2.css instead of the theme default.css.

This would work well with server side technology such as PHP or ASP.NET or whatever you like. Of course, you could potentially use javascript to save a cookie on the user computer to remember his choice and use javascript again to include the file that you remembered via the cookie.

If you want to let the user manage exactly what applies to specific elements of the design (such as the color of the header, the font, etc.) you could again, using a server-side technology (better in this case in my opinion) or javascript save things like header=blue, font=Arial and using jQuery apply what was stored to your page.

Hope it gives you an overview.

lpfavreau_359350

On a semi-related note, also see my answer about changing LESS variables which will result in updated CSS rules. Depending on your case that may be more useful since a single LESS variable can drive a lot of CSS rules.... https://stackoverflow.com/a/9491074/255961

user_2559610

not sure about changing the class properties I came here looking for an answer to that myself and seems there are a few answers for that already, as for saving you could use jquery $.post method to send a form containing changes or $.get with url encoded values to then write to the new css file using PHP fwrite, or file_put_contents. make sure you restrict access to this feature or ensure values meet a certain criteria before storing any data.

user_5119410

I am pretty sure you can't change the rules inside an existing style. Even firebug won't let you do this. You can style an element or set of elements, you can assign and unassign classes, but I don't think you can alter existing classes. In order to do what you are asking you will need to maintain some sort of associative array that records proposed changes to existing classes and then to save those changes you will need to upload to a server that can then offer a link for download to the client.

Scott_Evernden_113970
user_2479290
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