---
tags:
  - indexing
---

# Indexing

### `Fuse.createIndex`

Pre-generate the index from the list, and pass it directly into the Fuse instance. If the list is (considerably) large, it speeds up instantiation.

**Example**

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

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)
```

:::tip
Fuse will automatically index the table if one isn't provided during instantiation.
:::

### `Fuse.parseIndex`

Parses a serialized Fuse index.

**Example**

```js
// (1) In the build step
// Create the Fuse index
const myIndex = Fuse.createIndex(['title', 'author.firstName'], books)
// Serialize and save it
fs.writeFile('fuse-index.json', JSON.stringify(myIndex.toJSON()))

// (2) When app starts
// Load and deserialize index
const fuseIndex = await require('fuse-index.json')
const myIndex = Fuse.parseIndex(fuseIndex)
// initialize Fuse with the index
const fuse = new Fuse(books, options, myIndex)
```