Collections - Scripting in Java: Integrating with Groovy and JavaScript - page 216

Deleting Array Elements
Deleting an array element or nonelement properties of an array is the same as deleting
properties of an object. Use the delete operator to delete an array element. If you delete
an element from middle or beginning of a dense array, the array becomes sparse. The
following code shows how to delete elements from an array:
// Creates a dense array with elements at indexes 0, 1, and 2.
var names = new Array("Fu", "Li", "Do");
print("Before deleting:");
print("names.length = " + names.length + ", Elements = " + names);
// Delete the element at index 1
delete names[1]; // names.length remains 3
print("AFter deleting:");
print("names.length = " + names.length + ", Elements = " + names);
Before deleting:
names.length = 3, Elements = Fu,Li,Do
AFter deleting:
names.length = 3, Elements = Fu,,Do
You can make elements of an array nonconfigurable and nonwritable, so they cannot
be deleted and modified. Deleting a nonconfigurable element does not have any effect. In
strict mode, deleting a nonconfigurable element generates an error. The following code
demonstrates this:
var names = new Array("Fu", "Li", "Do");
// Make the element at index 1 non-configurable
Object.defineProperty(names, "1", {configurable: false});
print("Before deleting:");
print("names.length = " + names.length + ", Elements = " + names);
delete names[1]; // Will not delete "Li" as it is non-configurable.
print("AFter deleting:");
print("names.length = " + names.length + ", Elements = " + names);
Before deleting:
names.length = 3, Elements = Fu,Li,Do
AFter deleting:
names.length = 3, Elements = Fu,Li,Do