Using period to access object's property but undefined

Question

I am doing the codecademy's javascript tutorial and encountering the problem as following:

var friends = {};
friends.bill = {
  firstName: "Bill",
  lastName: "Gates",
  number: "(206) 555-5555",
  address: ['One Microsoft Way','Redmond','WA','98052']
};
friends.steve = {
  firstName: "Steve",
  lastName: "Jobs",
  number: "(408) 555-5555",
  address: ['1 Infinite Loop','Cupertino','CA','95014']
};
var list = function(obj){
    for(var prop in obj){
        console.log(prop);
    }
};
var search = function(name) {
  for(var prop in friends){ 
        console.log(prop);
        console.log(friends.prop);//friends[prop] will print out 

  }


};
list(friends);
search("Steve");

the console.log(friends.prop) will print out undefined but if I changed it to

friends[prop], it will print out the bill and steve object information.

I see the w3c tutorial say that two of the access method is right and I cannot figure out

what is the problem?

Thx in advance.

You'll need to use the bracket notation method when using variables with objects like that, so just use friends[prop] as friends.prop will never work. — adeneo
– adeneo, Commented Feb 24, 2013 at 19:17

ziesemer · Accepted Answer · 2013-02-24 19:18:26Z

2

The array notation ([prop]) is providing an additional level of indirection, a type of reflection.

So, friends.bill and friends["bill"] would be identical. But, if you want to do something like var prop = 'bill', then the only way to use this is as friends[prop].

If you try friends.prop, you're literally asking for it to look for a friend named "prop".

answered Feb 24, 2013 at 19:18

ziesemer

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