Javascript add blob to html input value

Question

I create a blob from an array containing base64 with zip.js

var strMsgArray = JSON.stringify(msgArray);
var blob = new Blob([strMsgArray], {
  type : "text/json;charset=utf-8"
});
zipBlob("message.json", blob, function(zippedBlob) {
    // do stuff
});

<input id="messageArray" type="hidden" />

This gives me the desired result in the console but now I need to add it to form input value and submit

It doesn't work as is. It doesn't work when I stringify. What is the correct way?