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<html><body><p>Click the button to create an OPTGROUP element.</p><button onclick="myFunction()">Try it</button><select id="mySelect" size="6"> <option>BMW <option>Mercedes <option>Ford <option>Volvo <option>Toyota</select><script>function myFunction() { var x = document.getElementById("mySelect"); var y = document.createElement("OPTGROUP"); y.setAttribute("label", "SwedishCars"); y.appendChild(x.options[3]) x.insertBefore(y, x.options[3]);}</script></body></html>