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# Method name: check(channel: Channel, subscriber: Subscriber)

# Method package: wixRealtimeBackend

# Method menu location: wixRealtimeBackend --> PermissionsRouter --> check

# Method Link: https://dev.wix.com/docs/velo/velo-only-apis/wix-realtime-backend/permissions-router/check.md

# Method Description:

Checks the permissions for a subscriber on a channel or channel resource.

The `check()` function returns a Promise that resolves to the permissions for the
 specified user on the specified channel or channel resource.

 The check is performed as follows:

 1. If a permissions handler for the specified channel or channel resource exists,
    it's invoked and its result is returned.
 1. If no handler is found for the specified channel resource, but a handler
    exists for the resource's channel, it's invoked and its result is returned.
 1. If no handler is found for the specified channel, but a default permissions handler
    exists, it's invoked and its result is returned.
 1. If the default handler has not been found, the default permissions are returned.

    The default permissions are:
    `{"read": true}`


 This function is typically called in the body of the
 [`realtime_check_permission()`](#realtime_check_permission) function like so:

 ```JavaScript
 export function realtime_check_permission(channel, subscriber) {
   return permissionsRouter.check(channel,subscriber);
 }
 ```



# Method Code Examples:

*** Note: do not assume any prop names or enum values other than the ones in the example.

## Check permission for a subscriber to a channel

```javascript
// In realtime-permissions.js

import {permissionsRouter} from 'wix-realtime-backend';

// ...

export function realtime_check_permission(channel, subscriber) {
  return permissionsRouter.check(channel,subscriber);
}
```

## Grant permissions for a channel based on subscriber type using the permissions router

```javascript
// In realtime-permissions.js

import {permissionsRouter} from 'wix-realtime-backend';

permissionsRouter.default( (channel, subscriber) => {
  return {"read": true};
} );

const membersOnlyChannel = {"name": "MembersOnly"};

permissionsRouter.add(membersOnlyChannel, (channel, subscriber) => {
  if(subscriber.type === "Member") {
    return {"read": true};
  }
  else {
    return {"read": false};
  }
});

export function realtime_check_permission(channel, subscriber) {
  return permissionsRouter.check(channel,subscriber);
}
```

## Grant permissions based on user data using the permissions router

```javascript
// In realtime-permissions.js

import { members } from `wix-members-backend`;
import { permissionsRouter } from 'wix-realtime-backend';

permissionsRouter.default((channel, subscriber) => {
  return {"read": true};
});

const membersOnlyChannel = {"name": "MembersOnly"};

permissionsRouter.add( membersOnlyChannel, async (channel, subscriber) => {
  let member = await members.getMember(subscriber.id, { fieldsets: ['FULL'] });
  
  if(channel.resourceId === "BobsOnly") {
    if(member.contactDetails.firstName === "Bob") {
      return { "read": true };
    }
    else {
      return { "read": false };
    }
  }
  else {
    return { "read": true };
  }
} );

export function realtime_check_permission(channel, subscriber) {
  return permissionsRouter.check(channel, subscriber);
}
```

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