string to hex string /hex string to string conversion

I put together this implementation using a byte array without having to copy and allocate new strings.

var buff = new Uint8Array(1024);

//ascii string to byte array
for (let i = 0; i < data.length; i++) {
      let c = ('0' + data.charCodeAt(i).toString(16)).slice(-2);
      buff[i * 2] = c.charCodeAt(0);
      buff[i * 2 + 1] = c.charCodeAt(1);
}

//Ascii string from byte Array - Note 'apply' only works for 64 arguments
function fromByteArray(len) {
      if (len < 64) return String.fromCharCode.apply(String, buff.slice(0,len));
      for (var result = [], i = 0; i < len; i += 64) {
            result.push(String.fromCharCode.apply(String, buff.slice(i, i + 64)));
      }
      return result.join("").slice(0,len); 
}

//Hex string to byte array
function toByteArray(data) {
      for (let i = 0; i < data.length/2; i++) {
            buff[i] = parseInt((data.substring(i*2,i*2+2)),16)
      }
      buff.slice(0,data.length /2);
}

After running a process.memory() command before and after these changes, I can't see any significant memory savings. Should we expect any improvements in memory usage by using a byte array, or does the string append provide the best use of memory allocation?

What improvements could we make to this implementation to improve memory allocation?