Blob of mintNFT'argument is not match front-side's input

[hokosugi]

I converted the string input value of front-size to Blob and used it as an argument to the mintNFTfunction to mint erc721-like nft, but got an error below.
I think metadeta value doesn't match blob variant, so need to match Blob type in motoko and blob in javascript.But I don't know what I do. What is needed? Thank you in advance.

error (chrome validation)

myNFT
index.js:17781 Blob {size: 5, type: 'text/html'}
index.js:17791 name::::myNFT
index.js:17793 miner::::rrkah-fqaaa-aaaaa-aaaaq-cai
index.js:4524 Uncaught (in promise) Error: Invalid record {to:variant {principal:principal; address:text}; metadata:opt vec nat8} argument: {"to":{"principal":{"_arr":{"0":0,"1":0,"2":0,"3":0,"4":0,"5":0,"6":0,"7":1,"8":1,"9":1},"_isPrincipal":true},"address":""},"metadeta":{}}
    at index.js:4524:19
    at index.js:3435:29
    at Array.map (<anonymous>)
    at zipWith (index.js:3435:15)
    at Module.encode (index.js:4522:75)
    at caller (index.js:199:74)
    at CanisterActor.handler [as mintNFT] (index.js:221:34)
    at HTMLButtonElement.<anonymous> (index.js:17798:99)
（匿名） @ index.js:4524
（匿名） @ index.js:3435
zipWith @ index.js:3435
encode @ index.js:4522
caller @ index.js:199
handler @ index.js:221
（匿名） @ index.js:17798

index.js (src/myNFT_assets)

document.getElementById("mintNftBtn").addEventListener("click", async () => {
  const nft = document.getElementById("nft").value.toString();
  console.log(nft);
  const blob = new Blob([nft], {type: 'text/html'});
  console.log(blob);
  function readAsText(b) {
    return new Promise((resolve, reject) => {
      let reader = new FileReader();
      reader.onload = () => { resolve(reader.result); };
      reader.onerror = () => { reject(reader.error); };
      reader.readAsText(b);
    });
  };
  const name = await readAsText(blob);
  console.log("name::::"+name);
  const minter = await dfinity_nft_ext.getMinter();
  console.log("miner::::"+minter);
  const mintReq = {
    to: { principal: minter, address: "" },
    metadeta: blob  // as execute, empty: "metadeta":{}
  };
  const minted = await dfinity_nft_ext.mintNFT(mintReq);  // mint
  console.log("minted::::"+minted);  //Maybe return minted number