Update browser version of HexEncoder parse()

lib/cryptoEngine.js

@@ -69,17 +69,22 @@ const HexEncoder = isNode
               if (!hexString) {
                   return null;
               }
-              if (hexString.length % 2 !== 0) throw "Invalid hexString";
+
-              const arrayBuffer = new Uint8Array(hexString.length / 2);
+              if (hexString.length % 2 !== 0) {
+                  throw new Error("Invalid hex string length");
+              }
+
+              const bytes = new Uint8Array(hexString.length / 2);
 
               for (let i = 0; i < hexString.length; i += 2) {
-                  const byteValue = parseInt(hexString.substring(i, i + 2), 16);
+                  const byte = parseInt(hexString.substring(i, i + 2), 16);
-                  if (isNaN(byteValue)) {
+                  if (isNaN(byte)) {
-                      throw "Invalid hexString";
+                      throw new Error("Invalid character in hex string.");
                   }
-                  arrayBuffer[i / 2] = byteValue;
+                  bytes[i / 2] = byte;
               }
-              return arrayBuffer;
+
+              return bytes;
           },
 
           /**
@@ -91,16 +96,10 @@ const HexEncoder = isNode
               if (!bytes) {
                   return null;
               }
-              const hexBytes = [];
 
-              for (let i = 0; i < bytes.length; ++i) {
+              return Array.from(bytes)
-                  let byteString = bytes[i].toString(16);
+                  .map((byte) => byte.toString(16).padStart(2, "0"))
-                  if (byteString.length < 2) {
+                  .join("");
-                      byteString = "0" + byteString;
-                  }
-                  hexBytes.push(byteString);
-              }
-              return hexBytes.join("");
           },
       };
 exports.HexEncoder = HexEncoder;