JS实现复制内容到剪贴板

function copyToClipboard(txt) {
  if (window.clipboardData) {
    window.clipboardData.clearData();
    window.clipboardData.setData("Text", txt);
  } else if (navigator.userAgent.indexOf("Opera") != -1) {
    window.location = txt;
  } else if (window.netscape) {
    try {
      netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
    } catch (e) {
      alert("被浏览器拒绝！\n请在浏览器地址栏输入'about:config'并回车\n然后将'signed.applets.codebase_principal_support'设置为'true'");
    }
    var clip = Components.classes['@mozilla.org/widget/clipboard;1'].createInstance(Components.interfaces.nsIClipboard);
    if (!clip)
      return;
    var trans = Components.classes['@mozilla.org/widget/transferable;1'].createInstance(Components.interfaces.nsITransferable);
    if (!trans)
      return;
    trans.addDataFlavor('text/unicode');
    var str = new Object();
    var len = new Object();
    var str = Components.classes["@mozilla.org/supports-string;1"].createInstance(Components.interfaces.nsISupportsString);
    var copytext = txt;
    str.data = copytext;
    trans.setTransferData("text/unicode", str, copytext.length * 2);
    var clipid = Components.interfaces.nsIClipboard;
    if (!clip)
      return false;
    clip.setData(trans, null, clipid.kGlobalClipboard);
    alert("复制成功！")
  }
}