---
title: Custom Behavior
order: 2
---

G6 provides abundant [Built-in Behavior](/en/docs/manual/middle/states/defaultBehavior). Besides, you can custom your type of behaviors to satisfy the special requirements.

In G6, we mainly take three scenarios into consideration:

- Demonstrating the relational data;
- Modeling the visualization;
- Analyzing the graph.

It is necessary to incorporate the interactions when the information is too complex to be understand in one glance:

- Zooming a large graph;
- Utilizing the ttoltip to show the detail information of a node;
- Adding/removing/modifying/querying a graph item.

Due to the complex and the diversity of the interactions in different scenarios and bussiness, we did not build all the interactions into G6:

- Some systems require to add nodes by clicking a tool bar, some require toe add by dragging from a panel;
- Some scenarios add edges by dragging from an anchor point, some add by clicking the end nodes;
- Some edges are allowed to link to any node, some only can be linked to specific anchor points;
- Some users require to custom the process of activating and endding.
- ...

We found the interactions are sundry and versatile. And the conflicts and configurations will make the users and developers collapse. Thus, G6 designs a set of simple and flexible implemention of interaction behavior.

## The Life Cycle of Behavior

To customize a Behavior, it is important to comprehend the life cycle of Behavior. Interaction Behaviors are related to the events from users, including the processes:

- Bind the event;
- Activate the event;
- Keep the event;
- End the event;
- Remove the event.

## registerBehavior

You can customize a Behavior by `G6.registerBehavior`. The following code implements a custom Behavior named `'activate-node'`, which changes the state `active` of the clicked node to be `true`, and restores the state `active` to be `false` when the user clicking the node again or clicking the canvas.

<span style="background-color: rgb(251, 233, 231); color: rgb(139, 53, 56)"> &nbsp;&nbsp;⚠️**Attension:** </span>

- The following code set the states for different behaviors, but does not assign the state styles for manipulated nodes. To change the styles when the states changed, refer to [State Styles](/en/docs/manual/middle/states/state).
- The configurations of customizing Behavior are introduced in [Behavior API](/en/docs/api/Behavior)；
- `getEvent` returns the events which are listened by the Behavior. The events in G6 are introduced in [Event API](/en/docs/api/Event).

```javascript
G6.registerBehavior('activate-node', {
  getDefaultCfg() {
    return {
      multiple: true
    };
  },
  getEvents() {
    return {
      'node:click': 'onNodeClick',
      'canvas:click': 'onCanvasClick'
    };
  }
  onNodeClick(e) {
    const graph = this.graph;
    const item = e.item;
    if (item.hasState('active')) {
      graph.setItemState(item, 'active', false);
      return;
    }
    // Get the configurations by this. If you do not allow multiple nodes to be 'active', cancel the 'active' state for other nodes
    if (!this.multiple) {
      this.removeNodesState();
    }
    // Set the 'active' state of the clicked node to be true
    graph.setItemState(item, 'active', true);
  },
  onCanvasClick(e) {
    // shouldUpdate can be overrode by users. Returning true means turning the 'active' to be false for all the nodes
    if (this.shouldUpdate(e, self)) {
      removeNodesState();
    }
  },
  removeNodesState() {
    graph.findAllByState('node', 'active').forEach(node => {
        graph.setItemState(node, 'active', false);
      });
  }
});
```

## Using Behavior

Now, you have a type of Behavior named `'activate-node'`. To use it, configure it into a mode of `modes` when instantiating a Graph. [Mode](/en/docs/manual/middle/states/mode). The following code configure the `'activate-node'` into the default mode, which means the `'activate-node'` Behavior will take effect in the default mode.

```javascript
const graph = new G6.Graph({
  container: 'mountNode',
  width: 500,
  height: 500,
  modes: {
    // Configure the custom Behavior here to use it
    default: ['activate-node'],
  },
});
```