JS复制对应id的内容到粘贴板（Ctrl+C效果）

<tr> <td> <a id="copy_{$key}" onclick="getUrl('{$key}')">复制文件链接</a> <input id="file_{$key}" value="{$file.file_url}" style="margin-left: -9999px"/> </td></tr> 

<pre><script type="application/javascript">  function getUrl(id) {  if (copyToClipboard(document.getElementById("file_"+id))){   alert("成功复制到黏贴板！");  }else{   alert("复制到黏贴板失败！");  } }  function copyToClipboard(elem) {  // create hidden text element, if it doesn't already exist  var targetId = "_hiddenCopyText_";  var isInput = elem.tagName === "INPUT" || elem.tagName === "TEXTAREA";  var origSelectionStart, origSelectionEnd;  if (isInput) {   // can just use the original source element for the selection and copy   target = elem;   origSelectionStart = elem.selectionStart;   origSelectionEnd = elem.selectionEnd;  } else {   // must use a temporary form element for the selection and copy   target = document.getElementById(targetId);   if (!target) {    var target = document.createElement("textarea");    target.style.position = "absolute";    target.style.left = "-9999px";    target.style.top = "0";    target.id = targetId;    document.body.appendChild(target);   }   target.textContent = elem.textContent;  }  // select the content  var currentFocus = document.activeElement;  target.focus();  target.setSelectionRange(0, target.value.length);   // copy the selection  var succeed;  try {   succeed = document.execCommand("copy");  } catch(e) {   succeed = false;  }  // restore original focus  if (currentFocus && typeof currentFocus.focus === "function") {   currentFocus.focus();  }   if (isInput) {   // restore prior selection   elem.setSelectionRange(origSelectionStart, origSelectionEnd);  } else {   // clear temporary content   target.textContent = "";  }  return succeed; }</script></pre>