为 Typecho 添加 Copy 按钮

        // 在代码块右上角添加复制按钮
        document.addEventListener('DOMContentLoaded', initCodeCopyButton);
        function initCodeCopyButton() {
            function initCSS(callback) {
                const css = `
                    .btn-code-copy {
                        position: absolute;
                        line-height: .6em;
                        top: .2em;
                        right: .2em;
                        color: rgb(87, 87, 87);
                    }
                    .btn-code-copy:hover {
                        color: rgb(145, 145, 145);
                        cursor: pointer;
                    }
                    `;
                const styleId = btoa('btn-code-copy').replace(/[=+\/]/g, '');
                const head = document.getElementsByTagName('head')[0];
                if (!head.querySelector('#' + styleId)) {
                    const style = document.createElement('style');
                    style.id = styleId;
                    if (style.styleSheet) {
                        style.styleSheet.cssText = css;
                    } else {
                        style.appendChild(document.createTextNode(css));
                    }
                    head.appendChild(style);
                }
                callback();
            };
            function copyTextContent(source) {
                let result = false;
                const target = document.createElement('pre');
                target.style.opacity = '0';
                target.textContent = source.textContent;
                document.body.appendChild(target);
                try {
                    const range = document.createRange();
                    range.selectNode(target);
                    window.getSelection().removeAllRanges();
                    window.getSelection().addRange(range);
                    document.execCommand('copy');
                    window.getSelection().removeAllRanges();
                    result = true;
                } catch (e) { console.log('copy failed.'); }
                document.body.removeChild(target);
                return result;
            };
            function initButton(pre) {
                const code = pre.querySelector('code');
                if (code) {
                    const preParent = pre.parentElement;
                    const newPreParent = document.createElement('div');
                    newPreParent.style = 'position: relative';
                    preParent.insertBefore(newPreParent, pre);
                    const copyBtn = document.createElement('div');
                    copyBtn.innerHTML = 'copy';
                    copyBtn.className = 'btn-code-copy';
                    copyBtn.addEventListener('click', () => {
                        copyBtn.innerHTML = copyTextContent(code) ? 'success' : 'failure';
                        setTimeout(() => copyBtn.innerHTML = 'copy', 250);
                    });
                    newPreParent.appendChild(copyBtn);
                    newPreParent.appendChild(pre);
                }
            };
            const pres = document.querySelectorAll('pre');
            if (pres.length !== 0) {
                initCSS(() => pres.forEach(pre => initButton(pre)));
            }
        };