File System Access API を使って Vue.js でObjectをjsonファイルにローカル保存。

jsonSave.ts

fileSave( output_obj:Object ) {
  let saveFileOptions = {
    suggestedName: "xxxxxx.json",
    types: [
      {
        description: "JSON Files",
        accept: {
          "application/json": [".json"],
        },
      },
    ],
  };

  (async () => {
    let blob = new Blob([JSON.stringify(output_obj, null, "  ")], {
      type: "application/json",
    });
    const handle = await window.showSaveFilePicker(saveFileOptions);
    await this.writeFile(handle, blob);
    console.log("save comp!!");
  })();
}

async writeFile(fileHandle, contents) {
  const writable = await fileHandle.createWritable();
  await writable.write(contents);
  await writable.close();
}