Conditional HTML classes

Written byPhuoc Nguyen

Created

06 Sep, 2022

The previous post introduces the technique to load styles for a given IE version. Let's revisit how the styles are organized:

<link href="styles.css" rel="stylesheet" />

<!--[if IE 8]>
    <link href="fix-ie8.css" rel="stylesheet" />
<![endif]-->

<!--[if IE 9]>
    <link href="fix-ie9.css" rel="stylesheet" />
<![endif]-->

As we can see, the approach adds one more HTTP request. For example, IE 8 will load `styles.css` and `fix-ie8.css` files as separate requests. We can reduce the number of requests by using the conditional comments for the root `html` element:

<!--[if lt IE 7]><html class="ie6"><![endif]-->
<!--[if IE 7]><html class="ie7"><![endif]-->
<!--[if IE 8]><html class="ie8"><![endif]-->
<!--[if IE 9]><html class="ie9"><![endif]-->
<!--[if (gt IE 9)|!(IE)]><!--><html><!--<![endif]--></html>

The root `html` element will have an additional CSS class depending on the current version of IE which visitors use. For example, IE 9 browser will add `ie9` CSS class. The styles are now combined into a single source

<link href="all-styles.css" rel="stylesheet" />

It contains the fixes for different IE versions:

.card {
    background: rgba(0, 0, 0, 0.5);
}

/* Background with opacity is only available on IE 9 and later */
.ie6 .card,
.ie7 .card,
.ie8 .card {
    background: #ccc;
}

The issue of the number of HTTP requests is resolved. However, the styles now contain many duplication codes. We can fix the issue by adding more CSS classes to the `html` element:

<!--[if lt IE 7]><html class="lt-ie7 lt-ie8 lt-ie9"><![endif]-->
<!--[if IE 7]><html class="lt-ie8 lt-ie9"><![endif]-->
<!--[if IE 8]><html class="lt-ie9"><![endif]-->
<!--[if gt IE 8]><!--><html><!--<![endif]--></html>

Additional styles for `card` on IE 6, 7, 8 now can be combined into a single class declaration:

.lt-ie9 .card {
    /* Styles for IEs before 9 */
}

Conditional comments←

Conditional HTML classes based on user agent→

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Phước Nguyễn

Conditional HTML classes

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