save_zip_to_local.js

 var bookBlob = new Blob([blob], {
     type: "application/zip"
 });
 // blob contains the zip file as a Blob object
 var fileReader = new FileReader();
 fileReader.onload = function (evt) {
     // Read out file contents as a Data URL
     var result = evt.target.result;
     try {
         localStorage.setItem("file", result);
     } catch (e) {
         console.log("Storage failed: " + e);
     }
 };
 // Load blob as Data URL
 fileReader.readAsDataURL(bookBlob);