speice.io/katex/contrib/copy-tex.mjs

// Set these to how you want inline and display math to be delimited.
var defaultCopyDelimiters = {
  inline: ['$', '$'],
  // alternative: ['\(', '\)']
  display: ['$$', '$$'] // alternative: ['\[', '\]']

}; // Replace .katex elements with their TeX source (<annotation> element).
// Modifies fragment in-place.  Useful for writing your own 'copy' handler,
// as in copy-tex.js.

function katexReplaceWithTex(fragment, copyDelimiters) {
  if (copyDelimiters === void 0) {
    copyDelimiters = defaultCopyDelimiters;
  }

  // Remove .katex-html blocks that are preceded by .katex-mathml blocks
  // (which will get replaced below).
  var katexHtml = fragment.querySelectorAll('.katex-mathml + .katex-html');

  for (var i = 0; i < katexHtml.length; i++) {
    var element = katexHtml[i];

    if (element.remove) {
      element.remove();
    } else if (element.parentNode) {
      element.parentNode.removeChild(element);
    }
  } // Replace .katex-mathml elements with their annotation (TeX source)
  // descendant, with inline delimiters.


  var katexMathml = fragment.querySelectorAll('.katex-mathml');

  for (var _i = 0; _i < katexMathml.length; _i++) {
    var _element = katexMathml[_i];

    var texSource = _element.querySelector('annotation');

    if (texSource) {
      if (_element.replaceWith) {
        _element.replaceWith(texSource);
      } else if (_element.parentNode) {
        _element.parentNode.replaceChild(texSource, _element);
      }

      texSource.innerHTML = copyDelimiters.inline[0] + texSource.innerHTML + copyDelimiters.inline[1];
    }
  } // Switch display math to display delimiters.


  var displays = fragment.querySelectorAll('.katex-display annotation');

  for (var _i2 = 0; _i2 < displays.length; _i2++) {
    var _element2 = displays[_i2];
    _element2.innerHTML = copyDelimiters.display[0] + _element2.innerHTML.substr(copyDelimiters.inline[0].length, _element2.innerHTML.length - copyDelimiters.inline[0].length - copyDelimiters.inline[1].length) + copyDelimiters.display[1];
  }

  return fragment;
}

function closestKatex(node) {
  // If node is a Text Node, for example, go up to containing Element,
  // where we can apply the `closest` method.
  var element = node instanceof Element ? node : node.parentElement;
  return element && element.closest('.katex');
} // Global copy handler to modify behavior on/within .katex elements.


document.addEventListener('copy', function (event) {
  var selection = window.getSelection();

  if (selection.isCollapsed || !event.clipboardData) {
    return; // default action OK if selection is empty or unchangeable
  }

  var clipboardData = event.clipboardData;
  var range = selection.getRangeAt(0); // When start point is within a formula, expand to entire formula.

  var startKatex = closestKatex(range.startContainer);

  if (startKatex) {
    range.setStartBefore(startKatex);
  } // Similarly, when end point is within a formula, expand to entire formula.


  var endKatex = closestKatex(range.endContainer);

  if (endKatex) {
    range.setEndAfter(endKatex);
  }

  var fragment = range.cloneContents();

  if (!fragment.querySelector('.katex-mathml')) {
    return; // default action OK if no .katex-mathml elements
  }

  var htmlContents = Array.prototype.map.call(fragment.childNodes, el => el instanceof Text ? el.textContent : el.outerHTML).join(''); // Preserve usual HTML copy/paste behavior.

  clipboardData.setData('text/html', htmlContents); // Rewrite plain-text version.

  clipboardData.setData('text/plain', katexReplaceWithTex(fragment).textContent); // Prevent normal copy handling.

  event.preventDefault();
});