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<!DOCTYPE html> <html> <body> <p id="p1">Select a value from the list below, to change this element's opacity!</p> <select onchange="myFunction(this);" size="5"> <option>0 <option>0.2 <option>0.5 <option>0.8 <option selected="selected">1 </select> <script> function myFunction(x) { // Return the text of the selected option var opacity = x.options[x.selectedIndex].text; var el = document.getElementById("p1"); if (el.style.opacity !== undefined) { el.style.opacity = opacity; } else { alert("Your browser doesn't support this example!"); } } </script> </body> </html>