blog - How to Add Copy to Clipboard Buttons to Code Blocks in Hugo - add-copy-buttons

add-copy-buttons.js

function addCopyButtons(clipboard) {
    document.querySelectorAll('pre > code').forEach(function (codeBlock) {
        var button = document.createElement('button');
        button.className = 'copy-code-button';
        button.type = 'button';
        button.innerText = 'Copy';

        button.addEventListener('click', function () {
            clipboard.writeText(codeBlock.innerText).then(function () {
                /* Chrome doesn't seem to blur automatically,
                   leaving the button in a focused state. */
                button.blur();

                button.innerText = 'Copied!';

                setTimeout(function () {
                    button.innerText = 'Copy';
                }, 2000);
            }, function (error) {
                button.innerText = 'Error';
            });
        });

        var pre = codeBlock.parentNode;
        if (pre.parentNode.classList.contains('highlight')) {
            var highlight = pre.parentNode;
            highlight.parentNode.insertBefore(button, highlight);
        } else {
            pre.parentNode.insertBefore(button, pre);
        }
    });
}