Is it possible to detect specific child node that changed?

Ionic Framework ionic-v3
1

Hello :slight_smile:

storeList 
 ㄴ3232390293(thes is uid)
    ㄴ point 
       ㄴ value1 : 500
       ㄴ value2 : 1000

above is my firebase database.

when value1 is changed to 700,
I want to detect in ionic app that value 1 is changed !

  //this.uid = 3232390293
 var a=this.afDb.list<Item>("/storeList/"+this.uid+"/point").valueChanges()
  a.subscribe((snap)=>{

    snap.map(item => {
      console.log(item);
    });
  })
  this.firedata.child(this.uid).child("point").on('value', (snap)=> {
    if(snap.val()!=null){
      console.log(snap.val()+"value changed!"+snap.key);
      for(var result in snap.val()){
          console.log(snap.val()[result]);
      }
    }
    });

but above code log is called whatever is changed under point node.
How can I detect only value that is changed?