javascript - Snapshot key not working with value findindex?

Question

How to make work findIndex depending of a snapshotkey ?it's not working with the variable but actually work with a manual string ?!

 this.state.data =     Object {

  "date_add": 1574177488383,
  "date_upd": 1574178141010,
  "question": "1",
"key": "123455566",
}
ref.on('child_changed', snapshot => {
          var key = snapshot.key


          console.log('the key', key) // return 123455566
})

actually not working like this :

      var foundIndex = this.state.data.findIndex(x => x.key == key); 

but work like this

 var foundIndex = this.state.data.findIndex(x => x.key == '123455566'); 

Answer 1

Waitting for answers