https://www.commandprompt.com/static/js/codehighlight.js

1hljs.addPlugin({
2    "after:highlightElement": ({ el, text }) => {
3        const wrapper = el.parentElement;
4        if (wrapper == null) {
5            return;
6        }
7
8        const copyButton = document.createElement("button");
9        copyButton.classList.add("code__copy");
10        let buttonTitle = 'Copy';
11        copyButton.innerHTML = buttonTitle;
12
13        copyButton.onclick = () => {
14            navigator.clipboard.writeText(text);
15            copyButton.innerHTML='Copied!';
16            setTimeout(() => {copyButton.innerHTML = buttonTitle}, 1500)
17        };
18        // Append the copy button to the wrapper
19        wrapper.appendChild(copyButton);
20    },
21});
22
23// Run `fn` over `items` in small time-boxed slices instead of one long loop,
24// so pages with several code blocks don't tie up the main thread in a single
25// multi-hundred-ms task (each hljs.highlightElement() call is a synchronous,
26// regex-heavy tokenize+render). Total work is unchanged -- this only breaks
27// it into scheduler-friendly chunks, improving TBT/INP without changing the
28// end result.
29function processInChunks(items, fn) {
30    const schedule = window.requestIdleCallback || ((cb) => setTimeout(cb, 0));
31    let i = 0;
32    function step() {
33        const start = performance.now();
34        while (i < items.length && performance.now() - start < 8) {
35            fn(items[i]);
36            i++;
37        }
38        if (i < items.length) {
39            schedule(step);
40        }
41    }
42    schedule(step);
43}
44
45// patch legacy code blocks from pre > content to pre > code > content
46// also, wrap legacy code blocks withinh code__wrapper div
47// (kept synchronous and cheap -- just element creation/insertion -- because
48// the highlighting pass below queries for its output and must see it in place)
49document.querySelectorAll('pre.code').forEach((el) => {
50    if (!el.querySelector('code')) {
51        const code = document.createElement('code');
52        code.textContent = el.textContent;
53        el.textContent = '';
54        el.appendChild(code);
55
56        const wrapper = document.createElement('div');
57        wrapper.classList.add("code__wrapper");
58        el.parentNode.insertBefore(wrapper, el);
59        wrapper.appendChild(el);
60    }
61});
62
63// The expensive part: highlight.js's regex-based tokenizing/rendering, run
64// once per block. Chunked so several code blocks don't stall the main
65// thread in one long task.
66processInChunks(document.querySelectorAll('pre > code'), (el) => {

67    hljs.highlightElement(el);
68});