add hw2

node_modules/katex/contrib/copy-tex/copy-tex.js

@@ -0,0 +1,51 @@
+// @flow
+
+import katexReplaceWithTex from './katex2tex';
+
+// Return <div class="katex"> element containing node, or null if not found.
+function closestKatex(node: Node): ?Element {
+    // If node is a Text Node, for example, go up to containing Element,
+    // where we can apply the `closest` method.
+    const element: ?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: ClipboardEvent) {
+    const selection = window.getSelection();
+    if (selection.isCollapsed || !event.clipboardData) {
+        return; // default action OK if selection is empty or unchangeable
+    }
+    const clipboardData = event.clipboardData;
+    const range = selection.getRangeAt(0);
+
+    // When start point is within a formula, expand to entire formula.
+    const startKatex = closestKatex(range.startContainer);
+    if (startKatex) {
+        range.setStartBefore(startKatex);
+    }
+
+    // Similarly, when end point is within a formula, expand to entire formula.
+    const endKatex = closestKatex(range.endContainer);
+    if (endKatex) {
+        range.setEndAfter(endKatex);
+    }
+
+    const fragment = range.cloneContents();
+    if (!fragment.querySelector('.katex-mathml')) {
+        return; // default action OK if no .katex-mathml elements
+    }
+
+    const 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();
+});