Store geometry change on modify interaction OpenLayers

Question

I am using OpenLayers modify interaction with events modifystart and modifyend. I am trying to remember state of feature before it is modified. I do it this way:

var modificirane_cestice=new Object()

modify.on('modifystart',function(e){
    e.features.forEach(function(feature){
        if(modificirane_cestice[ogc_fid]){
            return }
        else{
            modificirane_cestice[ogc_fid]=new Array()
            modificirane_cestice[ogc_fid].push(new ol.Feature({geometry:feature.getGeometry()}))
            }

    })
    })

 modify.on('modifyend',function(e){
    e.features.forEach(function(feature){
    izmjenjena_geometrija=feature.getGeometry()

    modificirane_cestice[ogc_fid].push(new ol.Feature({geometry:izmjenjena_geometrija}))
    posljednja_geometrija=modificirane_cestice[ogc_fid].length-1
    pg_pov=ol.sphere.getArea(modificirane_cestice[ogc_fid][0].getGeometry())
    zadnja_pov=ol.sphere.getArea(modificirane_cestice[ogc_fid][posljednja_geometrija].getGeometry())
    console.log(pg_pov+".... zadnja pov...."+zadnja_pov)
    postotak=pg_pov/zadnja_pov
    console.log(postotak)
    if(postotak<0.9){
        console.log("postotak prelazi 10% i iznosi: "+(1-postotak)*100+"%")
    }
    })
    })

I expected to get two different areas and features but in the end I got the same one. I know there is problem in referencing feature object but don't know how to solve it. I want to create a new object which are independent on their source object.

Answer 1

You need to use geometry:feature.getGeometry().clone() otherwise the features will share the same geometry object and a change to one will change both.