Javascript Array

You can access the contents of a simple variable just by using the variable’s name.
For example, alert(lastName) opens an alert box with the value stored in the variable
lastName. However, because an array can hold more than one value, you can’t just
use its name alone to access the items it contains. A unique number, called an index,
indicates the position of each item in an array. To access a particular item in an array,
you use that item’s index number. For example, say you’ve created an array with
abbreviations for the days of the week, and want to open an alert box that displayed
the first item.

var days = ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat', 'Sun'];
alert(days[0]);