Declaring arrays

    var myarray=["Bob", "Bully", "Amy"];

Sorting arrays

• It's done by array.sort()
• It's a method that's probably as much misunderstood as it is underestimated
• Sort's in ascending order. no direct way to sort in descending order

    var myarray=["Bob", "Bully", "Amy"];
    myarray.sort(); // Array now becomes ["Amy", "Bob", "Bully"]

• Sort's in lexicographical (aka alphabetical) order. Numeric sort not allowed

    var myarray=[7, 40, 300];
    myarray.sort();//Array now becomes [300,40,7]
    //Numerically 7<40<300 but lexicographically 7>40>300.
    //So we shouldn't use it for numeric sort. (array.reverse() may be used)

Customized Sorting of arrays

• Customized sort with a function argument to array.sort()
• The function should have 2 arguments
• The function should return integer value based on following conditions
  
  • Less than 0(negative): Sort "a" to be a lower index than "b".
  • Zero: "a" and "b" should be considered equal, and no sorting performed.
  • Greater than 0(positive): Sort "b" to be a lower index than "a".

    function sortfunction(a, b)
    {
        //Compare "a" and "b" in some fashion, and return -1, 0, or 1
    }
    var myarray=["Bob", "Bully", "Amy"];
    myarray.sort(sortfunction); //array will be sorted with fashion used.

• Sorting an array in numerical ascending

    var myarray=[25, 8, 7, 41];
    myarray.sort(function(a,b)
    {
        return a - b;
    }); //Array is [7, 8, 25, 41]

• Sorting an array in numerical descending

    var myarray=[25, 8, 7, 41];
    myarray.sort(function(a,b){
        return b - a;
    }); //Array is [41, 25, 8, 7]

• Shuffle array by Sorting an array randomly

    var myarray=[25, 8, 7, 41];
    myarray.sort(function()
    {
        return 0.5 - Math.random();
    }); //Array is now scrambled

Reversing array

1. It's done by array.reverse()
2. Will change the original array itself
3. if n is no.of.objects in array. Then object at x^th position will be swapped with (n-1)^th object.

    var myarray=["Bob", "Bully", "Amy"];
    myarray.reverse(); //Array now becomes ["Bully", "Bob", "Amy"]

Sort array alphabetically in descending order

1. Can be done with usage of sort and then reverse.

    var myarray=["Bob", "Bully", "Amy"]
    myarray.sort();
    myarray.reverse(); //Array now becomes ["Bully", "Bob", "Amy"]

Stack

1. A stack follows the Last-In First-Out (LIFO) paradigm
2. An item added last will be removed first.
3. The Array class has 2 methods that provide stack functionality. they are push() and pop().
   • push() appends an item to the end of the array
   • pop() removes and returns the last item in the array

    var stack = [];
    stack.push(2);  // stack is now [2]
    stack.push(5);  // stack is now [2, 5]
    var i = stack.pop(); // stack is now [2]
    alert(i);   // displays 5

Queue

1. A queue follows the First-In First-Out (FIFO) paradigm.
2. The first item added will be the first item removed.
3. The Array class has 2 methods that provide queue functionality. they are push() and shift().
   • push() inserts the passed argument at the end of the array.
   • shift() removes and returns the first item.

    var queue = [];
    queue.push(2);  // queue is now [2]
    queue.push(5);  // queue is now [2, 5]
    var i = queue.shift();  // queue is now [5];
    alert(i);   // displays 2

For Queue and Stack these function names may be confusing so we can always create aliases with our own names as below.

    var queue = [];
    queue.add = queue.push;
    queue.remove = queue.shift;
    queue.add(1);
    var i = queue.remove();
    alert(i);