Accessing Object Property Values with Dot and Bracket Notation.md

Accessing values in Objects.

Dot Notation is converting the value to a string (string literal). Example: myObj.name; is the same as myObj["name"]; and as we all know quotes define strings.

If you want to use a variable for accessing the value of object properties you cannot use Dot Notation. You have to use Bracket Notation. Example: var num = 42; myObj[num];

There are a few other limitations when accessing an object property. If the object key has a space or number in it, you cannot use dot notation.

var myObj = {
      "key one": "Value for 'key one'",
      "key": "Value for 'key'",
      "method property": "Method Property would be a function",
      "1": "Value for 'key 1'",
      "2": "Value for 'key 2'"
   };

For ease of explanation, I'm just returning strings for my object property values. The object property keys have a few different aspects to them, a couple with spaces and a couple as numbers.

When you use dot notation to access:

myObj.key one; The object value returned will be a string: "Value for 'key'"

Whereas, when you use bracket notation and access an object property key:

myObj["key one"]; The object value returned will be a string "Value for 'key one'".

If you try to use dot notation to access an object property with a space in it that doesn't have an additional corresponding shorter object property key. (Like I did with "key one" and "key")

You'll get the error: Uncaught SyntaxError: Unexpected identifier or SyntaxError: Unexpected token, expected ;

If you attempt to just do myObj.method; you will get back the value undefined

Additionally, if you were to access a number with dot notation:

myObj.1; .. You will get an error: Uncaught SyntaxError: Unexpected number or you may get SyntaxError: Unexpected token, expected ;

If you want to access an object property with a number as the object key you will be required to use Bracket Notation:

myObj["1"]; and you will get the object property value of "Value for 'key 1'".