# Add a JMap NG App extension
JMap NG extensions are plug-in modules taht can exetend the functionalities present in JMap NG App. You can develop and add your own extensions.
For more information about JMap NG extensions, refer to this [section](https://k2geospatial.github.io/jmap-app/latest/interfaces/jappextension.html).
The JMap NG App extension API documentation is available [here](https://k2geospatial.github.io/jmap-app/latest/interfaces/jappextension.html).
## A simple example
The example bellow shows a simple extension that creates a panel and displays some text on it.
Try it out in [Codepen.io](https://codepen.io/k2-dev/pen/RwxWozd?editors=1000)
```html
```
There is another way to load your extension, after the JMap NG App has been loaded.
You can register the previous extension like this:
```javascript
JMap.Application.Extension.register({
id: "my-extension",
panelIcon: "fas fa-wrench",
panelTitle: "My custom extension",
panelTooltip: "My custom extension",
onPanelCreation: containerId => {
const container = document.getElementById(containerId)
const span = document.createElement("span")
span.id = "my-text"
span.innerHTML = "This is a custom panel"
container.append(span)
},
onPanelDestroy: (containerId) => {
document.getElementById(containerId)
const text = document.getElementById("my-text")
if (text) {
text.remove()
}
}
})
```
## A more complete example
The example bellow shows you a more sophisticated extension named "Favourite locations".
It adds points on the map where you click, and displays a list of your "favourite" locations. You can also toggle the visibility of the point layer.
\
Try it out in [Codepen.io](https://codepen.io/k2-dev/pen/PoEPbVr)
```html
```
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