Navigator 3.0, Internet Explorer 3.0
The length property of an array is always one larger than the highest element defined in the array. For traditional "dense" arrays that have contiguous elements and begin with element 0, the length property specifies the number of elements in the array.
The length property of an array is initialized when the array is created with the Array() constructor method. Adding new elements to an array updates the length, if necessary:
a = new Array(); a.length initialized to 0 b = new Array(10); b.length initialized to 10 c = new Array("one", "two", "three"); c.length initialized to 3 c = "four"; c.length updated to 4 c = "blastoff"; c.length becomes 11