W3School TIY
编辑您的代码：
<!DOCTYPE html> <html> <head> <script> function ChangeOpacity(x) { // 返回被选选项的文本 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> </head> <body> <p id="p1">请从下面的例子中选择一个值，以改变此元素的不透明度。</p> <select onchange="ChangeOpacity(this);" size="5"> <option />0 <option />0.2 <option />0.5 <option />0.8 <option selected="selected" />1 </select> </body> </html>
查看结果: