JavaScript 2.0-The Complete Reference, Second ... - freecodingtutorial

Setting length to a value greater than the index of the last valid element has no effect on the
array contents, though it will increase the number of undefined slots in the array. Consider, for
example, the result of the following script,
var myArray = ["red", "green", "blue"];
myArray.length = 20;
alert("myArray="
which is shown here:
You shouldn‘t bother setting the length property directly, since the result of extending an array
is usually a sparsely populated array. However, deletion through this method is acceptable. For
example, removing the last element in the array with this capability is a bit unwieldy:
myArray.length = myArray.length - 1;
Newer versions of JavaScript provide a better way to remove the last element with methods the
Array object provides to simulate stacks and queues.
Arrays as Stacks and Queues
JavaScript 1.2+ and JScript 5.5+ provide methods for treating arrays like stacks and queues.
For those readers unfamiliar with these abstract data types, a stack is used to store data in lastin
first-out order, often called LIFO. That is, the first object placed in the stack is the last one
retrieved when the stack is read. A queue is an abstract data type used to store data in first-in
first-out order, also called FIFO. Data in a queue is retrieved in the order it was added.
A stack in the form of an array is manipulated using the push() and pop() methods. Calling
push() appends the given arguments (in order) to the end of the array and increments the
length property accordingly. Calling pop() removes the last element from the array, returns it,
and decrements the length property by one. An example of using the properties is as follows.
The contents of the array and any values returned are indicated in the comments.
var stack = []; // []
stack.push("first"); // ["first"]
stack.push(10, 20); // ["first", 10, 20]