How Can I Embed JavaScript Functionality in CSS?

Embedding JavaScript in CSS

While it's not directly possible to execute JavaScript within CSS, there are creative techniques that allow for similar functionality.

IE: Expression Technique and HTC Behavior

Internet Explorer provides two methods:

• Expression Technique: Involves creating an expression that evaluates a JavaScript expression. For example:

body {
  color: (function() { return document.getElementById("button").style.color; })();
}

• HTC Behavior: Utilizes a separate XML file (script.htc) loaded via CSS. Inside the HTC file, JavaScript can be executed.

body {
  behavior:url(script.htc);
}

<component tagname="xss">
   <attach event="ondocumentready" onevent="main()" literalcontent="false"></attach>
</component>

<script>
  function main() {
    alert("HTC script executed.");
  }
</script>

Firefox: XBL

Firefox offers a similar XML-based solution called XBL.

body {
  -moz-binding: url(script.xml#mycode);
}

<bindings xmlns="http://www.mozilla.org/xbl" xmlns:html="http://www.w3.org/1999/xhtml">

  <binding></binding></bindings>

Important Considerations

• JavaScript is executed only when the CSS selector matches an element in the document.
• These techniques are not standardized and may not work in all browsers.
• They can introduce security implications, so use cautiously.

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