making function to access object properties

Question

I am trying to write a common function to access object properties as parameters, but i keep getting "undefined". here is my code

var users = [{
  "id": 1,
  "first_name": "Fredelia",
  "last_name": "Tanman",
  "email": "[email protected]",
  "gender": "Female"
}, {
  "id": 2,
  "first_name": "Sigmund",
  "last_name": "Maryska",
  "email": "[email protected]",
  "gender": "Male"
}, {
  "id": 3,
  "first_name": "Axel",
  "last_name": "Stangoe",
  "email": "[email protected]",
  "gender": "Male"
}, {
  "id": 4,
  "first_name": "Mariana",
  "last_name": "Danneil",
  "email": "[email protected]",
  "gender": "Female"
}, {
  "id": 5,
  "first_name": "Kira",
  "last_name": "Papps",
  "email": "[email protected]",
  "gender": "Female"
}]

function getProp(prop){
      return users.map(function(person){
        return person.prop; 
      })
    }

https://jsbin.com/mirahavavi/edit?js,console