Hướng dẫn tạo button Codebox Sao chép và Chế độ Dark Mode

<script>
  /*<![CDATA[*/
  /* Codebox by House Of Blogger */
  (() => {
    /* config */
    var config = {
      copyText: 'Copy to Clipboard',
      copiedText: 'Copied to Clipboard',
      lightText: 'Switch to Light',
      darkText: 'Switch to Dark',
      copiedToast: 'Copied to Clipboard!'
    }
    /* main scripts */
    var cBox = document.querySelectorAll(".cBx");
    var dBdy = document.getElementsByTagName('body')[0];
    localStorage.getItem('CODE_MODE') === 'dark' ? dBdy.classList.add('cDrk') : dBdy.classList.remove('cDrk');
    for (var i = 0; i < cBox.length; i++){
      let c = cBox[i];
      c.setAttribute('data-code', i);
      c.insertAdjacentHTML("afterbegin", "<div class='cBxT'><button onclick='codeDark()'><svg class='line sun' viewBox='0 0 24 24'><circle cx='12' cy='12' r='5'></circle><line x1='12' y1='1' x2='12' y2='3'></line><line x1='12' y1='21' x2='12' y2='23'></line><line x1='4.22' y1='4.22' x2='5.64' y2='5.64'></line><line x1='18.36' y1='18.36' x2='19.78' y2='19.78'></line><line x1='1' y1='12' x2='3' y2='12'></line><line x1='21' y1='12' x2='23' y2='12'></line><line x1='4.22' y1='19.78' x2='5.64' y2='18.36'></line><line x1='18.36' y1='5.64' x2='19.78' y2='4.22'></line></svg><svg class='line moon' viewBox='0 0 24 24'><path d='M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z'></path></svg><span class='moon'>" + (config.darkText ? config.darkText : 'Dark Theme') + "</span><span class='sun'>" + (config.lightText ? config.lightText : 'Light Theme') + "</span></button><button onclick='codeCopy(" + i + ")'><svg class='line copy' viewBox='0 0 24 24'><rect x='9' y='9' width='13' height='13' rx='2' ry='2'></rect><path d='M5 15H4a2 2 0 0 1-2-2V4a2 2 0 0 1 2-2h9a2 2 0 0 1 2 2v1'></path></svg><svg class='line check' viewBox='0 0 24 24'><polyline points='9 11 12 14 22 4'></polyline><path d='M21 12v7a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h11'></path></svg><span class='copy'>" + (config.copyText ? config.copyText : 'Copy') + "</span><span class='check'>" + (config.copiedText ? config.copiedText : 'Copied') + "</span></button></div>");
    }
    window.codeDark = () => {
      localStorage.setItem("CODE_MODE", "dark" === localStorage.getItem("CODE_MODE") ? "light" : "dark");
      localStorage.getItem("CODE_MODE") === "dark" ? dBdy.classList.add("cDrk") : dBdy.classList.remove("cDrk");
    }
    window.codeCopy = (index) => {
      if (index !== undefined) {
        let el = document.querySelector(".cBx[data-code='" + index + "']");
        if (el !== null){
          let pre = el.querySelector('pre');
          if (pre !== null){
            var e = getSelection(),
                t = document.createRange();
            e.removeAllRanges();
            t.selectNodeContents(pre);
            e.addRange(t);
            document.execCommand("copy");
            e.removeAllRanges();
            el.classList.add('copied');
            toast(config.copiedToast ? config.copiedToast : 'Copied to clipboard');
            setTimeout(() => {
              el.classList.remove('copied');
            }, 2000)
          }
        }
      }
    }
  })()
  /*]]>*/
</script>