HTML表单特别效果—音量调节，购物数量

<form oninput="x.value=parseInt(a.value)+parseInt(b.value)">0
<input type="range" id="a" value="50">100
+<input type="number" id="b" value="50">
=<output name="x" for="a b"></output>
</form>

<p><strong>注意:</strong>  Internet Explorer 不支持 output 标签。</p>