<pre class="shiki github-dark shaku"><code>/** * @param {string} str - binary string * @returns {string} */function myBtoa(str) { const buffer = []; let res = ''; const base64Table = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'; while (str.length &gt; 0) { let first3char = str.slice(0,3); str = str.slice(3); let bits = ''; for (let char of first3char) { bits += char.charCodeAt(0).toString(2).padStart(8,'0'); } const buffer = []; let first6Bits = ''; while (bits.length &gt; 0) { first6Bits = bits.slice(0,6).padEnd(6,'0'); bits = bits.slice(6); const char = base64Table[parseInt(first6Bits, 2)]; buffer.push(char); } if (buffer.length &lt; 4) { buffer.push('='.repeat(4 - buffer.length)); } res += buffer.join(''); } return res;}</code></pre>

This is my accepted solution

btoa() accepts a binary string and returns a Base64-encoded ASCII string from it. Characters in a binary string are the ASCII character for each byte …