const promise = navigator.clipboard.writeText(newClipText);

<div id="content">123456</div>
<button id="copyButton">復(fù)制</button>

const copyButton = document.getElementById('copyButton');
const content = document.getElementById('content');
copyButton.addEventListener('click', function () {
  const selection = window.getSelection();
  const range = document.createRange();
  // 設(shè)置選中內(nèi)容
  range.selectNodeContents(content);
  // 清空選中內(nèi)容
  selection.removeAllRanges();
  // 添加選中內(nèi)容
  selection.addRange(range);
  document.execCommand('copy');
});

const copyButton = document.getElementById('copyButton');
const content = document.getElementById('content');
copyButton.addEventListener('click', function () {
  const selection = window.getSelection();
  const range = document.createRange();
  // 緩存用戶選中的內(nèi)容
  const currentRange =
    selection.rangeCount === 0 ? null : selection.getRangeAt(0);
  // 設(shè)置文檔片段
  range.selectNodeContents(content);
  // 清空選中內(nèi)容
  selection.removeAllRanges();
  // 將文檔片段設(shè)置為選中內(nèi)容
  selection.addRange(range);
  try {
    // 復(fù)制到剪貼板
    document.execCommand('copy');
  } catch (err) {
    // 提示復(fù)制失敗
  } finally {
    selection.removeAllRanges();
    if (currentRange) {
      // 還原用戶選中內(nèi)容
      selection.addRange(currentRange);
    }
  }
});

const copyButton = document.getElementById('copyButton');
const inputEl = document.getElementById('input');
copyButton.addEventListener('click', function () {
  const selection = window.getSelection();
  const currentRange =
    selection.rangeCount === 0 ? null : selection.getRangeAt(0);
  // 選中 input 內(nèi)容
  inputEl.select();
  // 復(fù)制到剪貼板
  try {
    document.execCommand('copy');
  } catch (err) {
    // 提示復(fù)制失敗
    // 。。。
  } finally {
    selection.removeAllRanges();
    if (currentRange) {
      // 還原用戶選中內(nèi)容
      selection.addRange(currentRange);
    }
  }
});

// Overwrite what is being copied to the clipboard.
document.addEventListener('copy', function (e) {
  // e.clipboardData is initially empty, but we can set it to the
  // data that we want copied onto the clipboard.
  e.clipboardData.setData('text/plain', '西炒蛋');
  // This is necessary to prevent the current document selection from
  // being written to the clipboard.
  e.preventDefault();
});