--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/katex/contrib/copy-tex.mjs	Wed Jun 17 21:43:52 2020 +0200
@@ -0,0 +1,85 @@
+// Set these to how you want inline and display math to be delimited.
+const 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.
+
+const katexReplaceWithTex = 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).
+  const katexHtml = fragment.querySelectorAll('.katex-mathml + .katex-html');
+
+  for (let i = 0; i < katexHtml.length; i++) {
+    const element = katexHtml[i];
+
+    if (element.remove) {
+      element.remove(null);
+    } else {
+      element.parentNode.removeChild(element);
+    }
+  } // Replace .katex-mathml elements with their annotation (TeX source)
+  // descendant, with inline delimiters.
+
+
+  const katexMathml = fragment.querySelectorAll('.katex-mathml');
+
+  for (let i = 0; i < katexMathml.length; i++) {
+    const element = katexMathml[i];
+    const texSource = element.querySelector('annotation');
+
+    if (texSource) {
+      if (element.replaceWith) {
+        element.replaceWith(texSource);
+      } else {
+        element.parentNode.replaceChild(texSource, element);
+      }
+
+      texSource.innerHTML = copyDelimiters.inline[0] + texSource.innerHTML + copyDelimiters.inline[1];
+    }
+  } // Switch display math to display delimiters.
+
+
+  const displays = fragment.querySelectorAll('.katex-display annotation');
+
+  for (let i = 0; i < displays.length; i++) {
+    const element = displays[i];
+    element.innerHTML = copyDelimiters.display[0] + element.innerHTML.substr(copyDelimiters.inline[0].length, element.innerHTML.length - copyDelimiters.inline[0].length - copyDelimiters.inline[1].length) + copyDelimiters.display[1];
+  }
+
+  return fragment;
+};
+
+document.addEventListener('copy', function (event) {
+  const selection = window.getSelection();
+
+  if (selection.isCollapsed) {
+    return; // default action OK if selection is empty
+  }
+
+  const fragment = selection.getRangeAt(0).cloneContents();
+
+  if (!fragment.querySelector('.katex-mathml')) {
+    return; // default action OK if no .katex-mathml elements
+  } // Preserve usual HTML copy/paste behavior.
+
+
+  const html = [];
+
+  for (let i = 0; i < fragment.childNodes.length; i++) {
+    html.push(fragment.childNodes[i].outerHTML);
+  }
+
+  event.clipboardData.setData('text/html', html.join('')); // Rewrite plain-text version.
+
+  event.clipboardData.setData('text/plain', katexReplaceWithTex(fragment).textContent); // Prevent normal copy handling.
+
+  event.preventDefault();
+});