[JS] Topic: Arrays (#8534)

* added documentation

* new change

* added changes

* added documentation

* Updated Changes

* Updated Documentation

* updated documentation

* updated

* added documentation

* updated documentation

JavaScript/Topics/5.Syntax/9.Arrays/Arrays.md

@@ -0,0 +1,121 @@
+# __Arrays__
+In JavaScript, array is a single variable that is used to store different elements. It is often used when we want to store list of elements and access them by a single variable. Unlike most languages where array is a reference to the multiple variable, in JavaScript array is a single variable that stores multiple elements.
+
+## __Declaring Array__
+
+There are basically two ways to declare an array.
+
+__Example:__
+``` js 
+var House = [ ]; // method 1 
+
+var House = new Array(); // method 2 
+```
+But generally method 1 is preferred over the method 2.
+
+## __Initialization of an Array__
+
+__Example (for Method 1):__
+``` js
+// Initializing while declaring
+var house = ["1BHK", "2BHK", "3BHK", "4BHK"];
+```
+__Example (for Method 2):__
+
+``` js
+
+// Initializing while declaring
+// Creates an array having elements 10, 20, 30, 40, 50
+var house = new Array(10, 20, 30, 40, 50);
+
+//Creates an array of 5 undefined elements
+var house1 = new Array(5);
+
+//Creates an array with element 1BHK
+var home = new Array("!BHK");
+
+```
+
+As shown in above example the house contains 5 elements i.e. (10 , 20, 30, 40, 50) while house1 contains 5 undefined elements instead of having a single element 5. Hence, while working with numbers this method is generally not preferred but it works fine with Strings and Boolean as shown in the example above home contains a single element 1BHK.
+We can also update after initialization. 
+
+```js
+// Creates an array of 4 undefined elements
+var house1 = new Array(4);
+
+// Now assign values
+house1[0] = "1BHK"
+house1[1] = "2BHK"
+house1[2] = "3BHK"
+house1[3] = "4BHK"
+```
+__An array in JavaScript can hold different elements.__
+
+We can store Numbers, Strings and Boolean in a single array. 
+
+__Example:__ 
+```js
+// Storing number, boolean, strings in an Array 
+var house = ["1BHK", 25000, "2BHK", 50000, "Rent", true]; 
+```
+
+## __Accessing Array Elements__ 
+Array in JavaScript are indexed from 0 so we can access array elements as follows:
+
+```js
+var house = ["1BHK", 25000, "2BHK", 50000, "Rent", true];
+alert(house[0]+" cost= "+house[1]);
+var cost_1BHK = house[1];
+var is_for_rent = house[5];
+alert("Cost of 1BHK = "+ cost_1BHK);
+alert("Is house for rent = ")+ is_for_rent);
+```
+## __Length property of an Array__
+Length property of an Array returns the length of an Array. Length of an Array is always one more than the highest index of an Array.
+
+__Example below illustrates the length property of an Array:__
+
+```js
+var house = ["1BHK", 25000, "2BHK", 50000, "Rent", true];
+
+//len contains the length of the array
+var len = house.length;
+for (var i = 0; i < len; i++)
+	alert(house[i]);
+
+```
+
+__Note :__ All the above examples can be tested by typing them within the script tag of HTML.
+
+
+## __Sorting Array Element__
+
+The index of the array elements determines the order in which values appear in an 
+array when a for loop is used to display the array.
+Sometimes you want values to 
+appear in sorted order, which means that strings will be presented alphabetically 
+and numbers will be displayed in ascending order.
+You can place an array in sorted order by calling the sort() method of the array object. __The sort()__ method reorders values assigned to elements of the array, regardless of the index of the element to which the value is assigned.
+Here’s what you need to do to sort an array:
+ 1. Declare the array.
+ 2. Assign values to elements of the array.
+ 3. Call the sort() method.
+
+
+## __More Array Methods__:
+1.The __slice()__ method takes a sequence of elements and uses them to create a new array.
+
+2.The __concat()__ method and __join()__ method transform elements into a string.
+
+3.The __shift()__ method removes and returns the first element of the array and then moves 
+the other elements up on the list.
+
+4.The __push()__ method creates a new element at the end of the array and assigns the value that you place between the parentheses of the new element.
+
+5.The __pop()__ method returns and removes the last element of the array.
+
+6.The __reverse()__ method is used to reverse the array from last to first element.
+
+<br>
+
+Contributor: [Utkarsha Kakade](https://github.com/utkarshakakade)