• In javascript arrays use numbered indexes. They don't have named indexes because javascript does not support associative arrays.
• In javascript object use name indexes.
• You should use objects when you want the element names to be strings (text).
• You should use arrays when you want the element names to be numbers.

Avoid new Array()
There is no need to use the JavaScript's built-in array constructor new Array().

Use [] instead.

These two different statements both create a new empty array named points:

var marks = new Array(); // Bad
var marks = []; // Good