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JavaScript

Posted by Felipe Granja
Felipe Granja
4,824 Points

Indexing Object Properties

Hi all!

I was doing some exercises online and came up with the following piece of code:

var search = function (name) {
  for (var key in friends) {
    if (name === friends[key].firstName) {
      console.log(friends[key]);
      return friends[key];
    }
  }
};

The code above works perfectly, but the one below doesn't:

var search = function (name) {
  for (var key in friends) {
    if (name === friends.key.firstName) {
      console.log(friends.key);
      return friends.key;
    }
  }
};

Can't I index object properties using both . as well as []?

Thanks in advance!

1 Answer

Leonardo Hernandez
Leonardo Hernandez
13,798 Points
Leonardo Hernandez
Leonardo Hernandez
13,798 Points

I think because your working variable 'key' is being treated as an integer by JavaScript. It works with the brackets because in that case the object property value is returned by its index.

Felipe Granja
Felipe Granja
4,824 Points

When I was testing the code to see what I was doing wrong, I saw that the value for 'key' were the properties of the object I was inspecting.

Anyway, I just read the following on Codecademy:

"An advantage of bracket notation is that we are not restricted to just using strings in the brackets. We can also use variables whose values are property names."

http://www.codecademy.com/courses/objects-ii/0/5?curriculum_id=506324b3a7dffd00020bf661

I guess that's the reason then since 'key' is just a variable to a property name.