# ArrivalListener

adjust whether element reach / leave the edge of viewport. Also can set offset.



## **initialize**

```javascript
new ArrivalListener({
  // options
});
```



## **options**

| 参数                      | 类型                               | 默认值             | 描述                                       |
| ----------------------- | -------------------------------- | --------------- | ---------------------------------------- |
| el                      | dom                              | (**necessary**) | element needs to listen to               |
| offsetTopEnterBottom    | number (px / percent) / function | 0               | offset when element's top enter viewport's bottom |
| offsetTopLeaveBottom    | number (px / percent) / function | 0               | offset when element's top leave viewport's bottom |
| offsetBottomReachTop    | number (px / percent) / function | 0               | offset when element's bottom enter / leave viewport's top |
| offsetBottomEnterBottom | number (px / percent) / function | 0               | offset when element's bottom enter viewport's bottom |
| offsetBottomLeaveBottom | number (px / percent) / function | 0               | offset when element's bottom leave viewport's bottom |
| onTopEnterBottom        | function                         | 0               | trigger when element's top enter viewport's bottom |
| onTopLeaveBottom        | function                         | null            | trigger when element's top leave viewport's bottom |
| onBottomEnterTop        | function                         | null            | trigger when element's bottom enter viewport's top |
| onBottomLeaveTop        | function                         | null            | trigger when element's bottom leave viewport's top |
| onBottomEnterBottom     | function                         | null            | trigger when element's bottom enter viewport's bottom |
| onBottomLeaveBottom     | function                         | null            | trigger when element's bottom leave viewport's bottom |