点击按钮把文本框的内容复制到剪切板的代码

  <input id="demo">
  <button onClick="demo.select();document.execCommand('copy')">copy</button>
  <button onClick="demo.createTextRange().execCommand('copy')">copy</button>
  <button onClick="window.clipboardData.setData('Text',demo.value)">copy</button>