使用javascript加载不同的CSS样式表

Question

I need to use javascript to load a different stylesheet based on a URL variable that is being passed.

The scenario is this: We need to maintain a mobile website with one CSS stylesheet, and a different stylesheet that will be used to style the same page when it is accessed via a web-view loaded in an iOS app.

If you look at www.blog.meetcody.com you'll see that we're already using media queries and responsive webdesign. The reason that this is insufficient for us is because media queries cannot detect if the page is being loaded via a webview in a native app vs. a mobile safari. We need to handle these two cases separately. The blog is a hosted wordpress blog, that we are accessing via a JSON API in our iOS app.

The way we are handling this is as follows: When the webpage is loaded via our iOS app, we append a variable to the end of the URL "/?app=true". What I'd like to do is check to see if the URL contains this string, and if so, use a different webview.

I am attempting to do this with the below code:

    <script language="javascript" type="text/javascript">
    if(window.location.href.indexOf('/?app=true') > -1) {

        document.write("<link rel=\"stylesheet\" type=\"text/css\" href=\"http://blog.meetcody.com/wp-content/themes/standard/appstyle.css\" />");
    }
    document.close(); 
</script>

The issue that I'm having is that the above code doesn't actually load the appstyle.css stylesheet when ?app=true is part of the URL.

If you take a look at http://blog.meetcody.com/wp-content/themes/standard/appstyle.css?ver=3.4.2 you can see that I'm testing this by setting the background: black in the body {} tag

body {
background: black;
}

Whereas, in style.css at http://blog.meetcody.com/wp-content/themes/standard/style.css?ver=3.4.2 the body background color is #F2F0EB; in the body {} tag

    body {
        background: #F2F0EB;
   }

Of course, we want to do more than just change the background color, but I'm just showing this as an example.

Is there a better way to do this, or is there something wrong with my code? Perhaps I cannot use a direct link to appstyle.css an href in javascipt? Help much appreciated. And Merry Christmas!

Answer 1

You can add a CSS stylesheet by using appendChild() like this:

 var header = $.getElementsByTagName('head')[0];
 var styleSheet = $.createElement('link');
 styleSheet.rel = 'stylesheet';
 styleSheet.type = 'text/css';
 styleSheet.href = 'style.css'; // name of your css file
 styleSheet.media = 'all';
 header.appendChild(styleSheet);

Of course you could change this example to accomodate different css file names depending on the current URL by doing something like this:

 styleSheet.href = (isMobile == true) ? 'mobile.css' : 'default.css';

Answer 2

You should never try to close the document when you use inline script. document.close is only needed if you document.write to an iframe, frame or new window

Also I suggest you test the location.search rather than the href since that is where you placed the flag.

Please try

<script language="javascript" type="text/javascript">
if (location.search.indexOf('app=true') > -1) {
  document.write('<link rel="stylesheet" type="text/css" href="http://blog.meetcody.com/wp-content/themes/standard/appstyle.css" />');
}
</script>

and possibly place that script AFTER the other stylesheets, if you want to override stuff set in one of your 10+ sheets at your site, or better: test the query string on the server, or where you set the query string to app=yes, set something in the session or similar and use that to include the correct css on the server instead of relying on JS

PS: Your body tag has the classes of home and blog on your homepage. I suggest you look to the above mentioned stylesheets and see what the colour is in those for those classes.

PPS: I do not see any media detection here

<link rel='stylesheet' id='standard-activity-tabs-css'  href='/wp-content/themes/standard/lib/activity/css/widget.css?ver=3.4.2' type='text/css' media='all' />
<link rel='stylesheet' id='gcse-widget-css'  href='/wp-content/themes/standard/lib/google-custom-search/css/widget.css?ver=3.4.2' type='text/css' media='all' />
<link rel='stylesheet' id='standard-ad-300x250-widget-css'  href='/wp-content/themes/standard/lib/standard-ad-300x250/css/widget.css?ver=3.4.2' type='text/css' media='all' />
<link rel='stylesheet' id='standard-ad-125x125-widget-css'  href='/wp-content/themes/standard/lib/standard-ad-125x125/css/widget.css?ver=3.4.2' type='text/css' media='all' />
<link rel='stylesheet' id='standard-ad-468x60-css'  href='/wp-content/themes/standard/lib/standard-ad-billboard/css/widget.css?ver=3.4.2' type='text/css' media='all' />
<link rel='stylesheet' id='standard-personal-image-widget-css'  href='/wp-content/themes/standard/lib/personal-image/css/widget.css?ver=3.4.2' type='text/css' media='all' />
<link rel='stylesheet' id='standard-influence-css'  href='/wp-content/themes/standard/lib/influence/css/widget.css?ver=3.4.2' type='text/css' media='all' />
<link rel='stylesheet' id='bootstrap-css'  href='/wp-content/themes/standard/css/lib/bootstrap.css?ver=3.4.2' type='text/css' media='all' />
<link rel='stylesheet' id='bootstrap-responsive-css'  href='/wp-content/themes/standard/css/lib/bootstrap-responsive.css?ver=3.4.2' type='text/css' media='all' />
<link rel='stylesheet' id='standard-css'  href='/wp-content/themes/standard/style.css?ver=3.4.2' type='text/css' media='all' />