Why can I add named properties to an array as if it were an object?

Question

The following two different code snippets seem equivalent to me:

var myArray = Array();
myArray[\'A\'] = \"Athens\";
myArray[\'B\'] = \"Berlin\";


        

Answer 1

The difference between the arrays and the other objects in JavaScript. While arrays have a magically updating length property, for objects other than the arrays there is no way to implement such a property.

var arrName = [];
arrName[5] = "test";
arrName.length; // <- 6

Array are used to store things with an ordinal index - use it like a traditional array, stack, or queue. An object is a hash - use it for data that has a distinct key.