fuse.js

const options = { keys: ['title', 'author.firstName'] }

// Create the Fuse index
const myIndex = Fuse.createIndex(options.keys, books)

// initialize Fuse with the index
const fuse = new Fuse(books, options, myIndex)

// Output 
const list = [
  {
    "title": "Old Man's War",
    "author": {
      "firstName": "John",
      "lastName": "Scalzi"
    }
  },
  {
    "title": "The Lock Artist",
    "author": {
      "firstName": "Steve",
      "lastName": "Hamilton"
    }
  }
  /*...*/
]