我正在使用隐藏文本区域放置一些文本,选择它然后使用document.execCommand将其复制到剪贴板.这通常有效但在文本很大时失败(返回false).在Chrome v55中,它似乎在180K字符左右失败.

可以通过这种方式复制的数据量是否有限制？正常Ctrl C似乎不受相同的限制.

注意：有人将此标记为Does document.execCommand(‘copy’) have a size limitation?的可能副本.这可能是类似的问题,但是那个被标记为我不使用的特定框架,而且,它没有被回答.我相信我的问题更为笼统,仍然具有相关性.

我附上代码以供参考.

      function copyTextToClipboard(text) {
        var textArea = document.createElement('textarea');
        textArea.style.position = 'fixed';
        textArea.style.top = 0;
        textArea.style.left = 0;
        textArea.style.width = '2em';
        textArea.style.height = '2em';
        textArea.style.padding = 0;
        textArea.style.border = 'none';
        textArea.style.outline = 'none';
        textArea.style.boxShadow = 'none';
        textArea.style.background = 'transparent';
        textArea.value = text;
        document.body.appendChild(textArea);
        textArea.select();
        try {
          var successful = document.execCommand('copy');
          var msg = successful ? 'successful' : 'unsuccessful';
          console.log('Copying text command was ' + msg);
        } catch (err) {
          console.log('Oops, unable to copy');
        }
        document.body.removeChild(textArea);
      }

解决方法:

问题与渲染这个长文本所花费的时间有关,而不是execCommand(‘copy’)调用本身.

Firefox提出了一个非常明确的错误消息：

document.execCommand(‘cut’/‘copy’) was denied because it was not called from inside a short running user-generated event handler.

您的代码生成文本所需的时间太长,因此浏览器不会将其识别为半可信事件…

然后解决方案是首先生成此文本,并且仅在收听用户手势以调用execCommand之后.为了使它成为可能,你可以例如听一个mousedown事件来生成文本,只有在mouseup事件中才能真正执行copy命令.

const text = ('some text a bit repetitive ' + Date.now()).repeat(50000);

function copyTextToClipboard(text) {
  // first we create the textArea
  var textArea = document.createElement('textarea');
  textArea.style.position = 'absolute';
  textArea.style.opacity = '0';
  textArea.value = text;
  document.body.appendChild(textArea);

  var execCopy = e => {   // triggered on mouseup
    textArea.select();
    var successful = document.execCommand('copy');
    var msg = successful ? 'successful' : 'unsuccessful';
    console.log('Copying text command was ' + msg);
    document.body.removeChild(textArea);
  };
  // here the magic
  btn.addEventListener('mouseup', execCopy, {
    once: true 
  });
}
// triggered on mousedown
btn.onmousedown = e => copyTextToClipboard(text);

<button id="btn">copy some text in your clipboard</button>
<p>May struggle your browser a little bit, it's quite a long text... Please be patient</p>