This is a continuation of a series introducing data structures in javascript. In the last couple ofposts, the javascript Array was introduced and it is recommended to have an understanding of thejavascript Array before reading this article.StackA stack is a linear data structure and abstract data type in which operations are performed via thelast in, first out (LIFO) methodology. Similar to other programming languages there are two mainmethods in javascript used to populate and retrieve data in the stack. These methods are 'push' and 'pop'. The 'push' method is used to add an element to the top of stack and the 'pop' method isused to remove the top element from the stack.In javascript, the Array object is used for a stack implementation. Javascript has a push() and a pop() method for the Array object which makes the implementation rather simple.[sourcecode language="javascript"] var stack = new Array(); stack.push("one"); stack.push("two"); stack.push("three"); document.writeln(stack.pop() + " - stack length:" + stack.length); // prints "three - stack length: 2" document.writeln(stack.pop() + " - stack length:" + stack.length); // prints "two - stack length: 1" document.writeln(stack.pop() + " - stack length:" + stack.length); // prints "one - stack length: 0" [/sourcecode]One key point to understand is that when pushing an element to the stack it is adding it to the endof the Array. This may be counter intuitive since it is commonly referred to as the "top of the stack".Another point to understand is that when you use the pop method it removes the last element from theArray as indicated in the code sample when it prints the Array length.QueueA queue is also a linear data structure and abstract data type with one key difference from a stackbeing that it uses a first in, first out (FIFO) methodology. Another name for a queue is a buffer.Typical usage of a queue would be for instances where you have more data to manipulate than you canhandle in a single period of time.In javascript, the Array object is also used for a queue implementation. The unshift() method isused to add elements to the beginning of an Array; ensuring that when you use pop() you get the firstelement that was added to the Array.[sourcecode language="javascript"] var queue = []; queue.unshift("one"); queue.unshift("two"); queue.unshift("three"); document.writeln(queue.pop() + " - queue length:" + queue.length); // prints "one - queue length: 2" document.writeln(queue.pop() + " - queue length:" + queue.length); // prints "two - queue length: 1" document.writeln(queue.pop() + " - queue length:" + queue.length); // prints "three - queue length: 0" [/sourcecode]