# Advanced configuration

# Reactivity

When the FacilMap server sends an event to the client that an object has been created, changed or deleted, the client emits the event and also persists it in its properties. So you have two ways to access the map data: By listening to the map events and persisting the data somewhere else, or by accessing the properties on the Client object.

If you are using a UI framework that relies on a change detection mechanism (such as Vue.js or Angular), you can override the methods _set and _delete. facilmap-client consistently uses these to update any data on its properties.

In Vue.js, it could look like this:

const client = new Client("https://facilmap.org/");
client._set = Vue.set;
client._delete = Vue.delete;

In Angular.js, it could look like this:

const client = new Client("https://facilmap.org/");
client._set = (object, key, value) => { $rootScope.$apply(() => { object[key] = value; }); };
client._delete = (object, key) => { $rootScope.$apply(() => { delete object[key]; }); };

This way your UI framework will detect changes to any properties on the client, and you can reference values like client.padData.name, client.disconnected and client.loading in your UI components.

Note that client always replaces whole objects rather than updating individual properties. For example, when a new version of the map settings arrives, client.padData is replaced with a new object, or when a new marker arrives, client.markers[markerId] is replaced with a new object. This makes deep watches unnecessary in most cases.

# Marker/line data

The data of a marker or a line maps the name of a field (for example Description) to a value. Since field names are user-defined, a user could potentially set field names that are at risk to cause errors or even prototype pollution in JavaScript, such as __proto__, constructor or toString. To avoid such problems, the data property is a null prototype object by default.

In some situations, using a null prototype object might not be enough. For example, Vue 2’s reactivity system adds an __ob property to all objects. To handle such cases, facilmap-client allows to use a custom type for the data property by specifying the _encodeData and _decodeData methods to translate the data objects from a null prototype object to a custom type and back.

The following example uses an ES6 Map (opens new window) for the data:

const client = new Client("https://facilmap.org/");
client._decodeData = (data) => new Map(Object.entries(data));
client._encodeData = (data) => Object.fromEntries([...data]);

Doing this will change the type of the data property of the Marker and Line types in all properties, methods and events that deal with such objects.

In TypeScript, you can specify the data type using a generic (Client<Map<string, string>>).