I used the fallowing code to show a popup over marker in app. I need to add a nice button on popup.
map.on('dragend',(MouseEvent) =>{
this.Getaddress(map.getCenter()).then(data => {
var popup = Leaflet.popup()
.setLatLng(map.getCenter())
.setContent('<h2>' + data + '</h2>' + '<br />' + '<p>Hello world!<br />This is a nice popup.</p>' +'<button ion-button clear round (click)=" openPosting()" ')
.openOn(map);
});