# Guide

[中文指南](./guide.zh_CN.md)

## Installation

### Direct `<script>` include

You are recommended to install rrweb via jsdelivr's CDN service:

```html
<link
  rel="stylesheet"
  href="https://cdn.jsdelivr.net/npm/rrweb@latest/dist/rrweb.min.css"
/>
<script src="https://cdn.jsdelivr.net/npm/rrweb@latest/dist/rrweb.min.js"></script>
```

Also, you can link to a specific version number that you can update manually:

```html
<script src="https://cdn.jsdelivr.net/npm/rrweb@0.7.0/dist/rrweb.min.js"></script>
```

#### Only include the recorder code

rrweb's code includes both the record and the replay parts. Most of the time you only need to include the record part into your targeted web Apps.
This also can be done by using the CDN service:

```html
<script src="https://cdn.jsdelivr.net/npm/rrweb@latest/dist/record/rrweb-record.min.js"></script>
```

### NPM

```shell
npm install --save rrweb
```

rrweb provides both commonJS and ES modules bundles, which is easy to use with the popular bundlers.

### Compatibility Note

rrweb does **not** support IE11 and below, because it uses the `MutationObserver` API which was supported by [these browsers](https://caniuse.com/#feat=mutationobserver).

## Getting Started

### Record

**If you only included the record code with `<script>`**, then you must use the global variable `rrwebRecord` instead of `rrweb.record`.
The following sample code will use the variable `rrweb` which is the default exporter of this library.

```js
rrweb.record({
  emit(event) {
    // store the event in any way you like
  },
});
```

During recording, the recorder will emit when there is some event incurred, all you need to do is to store the emitted events in any way you like.

The `record` method returns a function which can be called to stop events from firing:

```js
let stopFn = rrweb.record({
  emit(event) {
    if (events.length > 100) {
      // stop after 100 events
      stopFn();
    }
  },
});
```

A more real-world usage may looks like this:

```js
let events = [];

rrweb.record({
  emit(event) {
    // push event into the events array
    events.push(event);
  },
});

// this function will send events to the backend and reset the events array
function save() {
  const body = JSON.stringify({ events });
  events = [];
  fetch('http://YOUR_BACKEND_API', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body,
  });
}

// save events every 10 seconds
setInterval(save, 10 * 1000);
```

#### Privacy

You may find some contents on the webpage which are not willing to be recorded, then you can use the following approaches:

- An element with the class name `.rr-block` will not be recorded. Instead, it will replay as a placeholder with the same dimension.
- An element with the class name `.rr-ignore` will not record its input events.
- `input[type="password"]` will be ignored as default.

#### Checkout

By default, all the emitted events are required to replay a session and if you do not want to store all the events, you can use the checkout config.

**Most of the time you do not need to configure this**. But if you want to do something like capturing just the last N events from when an error has occurred, here is an example:

```js
// We use a two-dimensional array to store multiple events array
const eventsMatrix = [[]];

rrweb.record({
  emit(event, isCheckout) {
    // isCheckout is a flag to tell you the events has been checkout
    if (isCheckout) {
      eventsMatrix.push([]);
    }
    const lastEvents = eventsMatrix[eventsMatrix.length - 1];
    lastEvents.push(event);
  },
  checkoutEveryNth: 200, // checkout every 200 events
});

// send last two events array to the backend
window.onerror = function() {
  const len = eventsMatrix.length;
  const events = eventsMatrix[len - 2].concat(eventsMatrix[len - 1]);
  const body = JSON.stringify({ events });
  fetch('http://YOUR_BACKEND_API', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body,
  });
};
```

Due to the incremental-snapshot-chain mechanism rrweb used, we can not capture the last N events accurately. With the sample code above, you will finally get the last 200 to 400 events been sent to your backend.

Similarly, you can also configure `checkoutEveryNms` to capture the last N minutes events:

```js
// We use a two-dimensional array to store multiple events array
const eventsMatrix = [[]];

rrweb.record({
  emit(event, isCheckout) {
    // isCheckout is a flag to tell you the events has been checkout
    if (isCheckout) {
      eventsMatrix.push([]);
    }
    const lastEvents = eventsMatrix[eventsMatrix.length - 1];
    lastEvents.push(event);
  },
  checkoutEveryNms: 5 * 60 * 1000, // checkout every 5 minutes
});

// send last two events array to the backend
window.onerror = function() {
  const len = eventsMatrix.length;
  const events = eventsMatrix[len - 2].concat(eventsMatrix[len - 1]);
  const body = JSON.stringify({ events });
  fetch('http://YOUR_BACKEND_API', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body,
  });
};
```

With the sample code above, you will finally get the last 5 to 10 minutes of events been sent to your backend.

### Replay

You need to include the style sheet before replay:

```html
<link
  rel="stylesheet"
  href="https://cdn.jsdelivr.net/npm/rrweb@latest/dist/rrweb.min.css"
/>
```

And then initialize the replayer with the following code:

```js
const events = YOUR_EVENTS;

const replayer = new rrweb.Replayer(events);
replayer.play();
```

#### Options

The replayer accepts options as its constructor's second parameter, and it has the following options:

| key          | default       | description                                     |
| ------------ | ------------- | ----------------------------------------------- |
| speed        | 1             | replay speed ratio                              |
| root         | document.body | the root element of replayer                    |
| loadTimeout  | 0             | timeout of loading remote style sheet           |
| skipInactive | false         | whether to skip inactive time                   |
| showWarning  | true          | whether to print warning messages during replay |

#### Use rrweb-player

Since rrweb's replayer only provides a basic UI, you can choose rrweb-replayer which is based on rrweb's public APIs but has a feature-rich replayer UI.

##### Installation

rrweb-player can also be included with `<script>`：

```html
<link
  rel="stylesheet"
  href="https://cdn.jsdelivr.net/npm/rrweb-player@latest/dist/style.css"
/>
<script src="https://cdn.jsdelivr.net/npm/rrweb-player@latest/dist/index.js"></script>
```

Or installed by using NPM：

```shell
npm install --save rrweb-player
```

##### Usage

```js
new rrwebPlayer({
  target: document.body, // customizable root element
  data: {
    events,
  },
});
```

#### Events

Developers may want to extend the rrweb's replayer or respond to its events. Such as giving a notification when the replayer starts to skip inactive time.
So rrweb expose a public API `on` which allow developers listen to the events and customize the reactions, and it has the following events:

| event                  | description                        |
| ---------------------- | ---------------------------------- |
| start                  | started to replay                  |
| pause                  | paused the replay                  |
| resume                 | resumed the replay                 |
| finish                 | finished the replay                |
| fullsnapshot-rebuilded | rebuilded a full snapshot          |
| load-stylesheet-start  | started to load remote stylesheets |
| load-stylesheet-end    | loaded remote stylesheets          |
| skip-start             | started to skip inactive time      |
| skip-end               | skipped inactive time              |

The rrweb-replayer also re-expose the event listener via  a `component.addEventListener` API.

## API

### rrweb

#### rrweb.record

```typescript
type record = (options: recordOptions) => listenerHandler;

type recordOptions = {
  emit: (e: eventWithTime) => void;
};
type listenerHandler = () => void;
```

#### rrweb.Replayer

```typescript
class Replayer {
  public wrapper: HTMLDivElement;

  constructor(events: eventWithTime[], config?: Partial<playerConfig>);

  public on(event: string, handler: mitt.Handler): void;
  public setConfig(config: Partial<playerConfig>): void;
  public getMetaData(): playerMetaData;
  public getTimeOffset(): number;
  public play(timeOffset?: number): void;
  public pause(): void;
  public resume(timeOffset?: number): void;
}

type playerConfig = {
  speed: number;
  root: Element;
  loadTimeout: number;
  skipInactive: Boolean;
};

type playerMetaData = {
  totalTime: number;
};
```

## REPL tool

You can also play with rrweb by using the REPL testing tool which does not need installation.

Run `npm run repl` to launch a browser and ask for a URL you want to test on the CLI:

```
Enter the url you want to record, e.g https://react-redux.realworld.io:
```

Waiting for the browser to open the specified page and print the following messages on the CLI:

```
Enter the url you want to record, e.g https://react-redux.realworld.io: https://github.com
Going to open https://github.com...
Ready to record. You can do any interaction on the page.
Once you want to finish the recording, enter 'y' to start replay:
```

At this point, you can interact in the web page. After the desired operations have been recorded, enter 'y' on the CLI, and the test tool will replay the operations to verify whether the recording was successful.

The following messages will be printed on the CLI during replay:

```
Enter 'y' to persistently store these recorded events:
```

At this point, you can enter 'y' again on the CLI. The test tool will save the recorded session into a static HTML file and prompt for the location:

```
Saved at PATH_TO_YOUR_REPO/temp/replay_2018_11_23T07_53_30.html
```

This file uses the latest rrweb bundle code, so we can run `npm run bundle:browser` after patching the code, then refresh the static file to see and debug the impact of the latest code on replay.