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object : Objects in JavaScript, just as in many other programming languages, can be compared to objects in real life. 
         The concept of objects in JavaScript can be understood with real life, tangible objects.
         In JavaScript, an object is a standalone entity, with properties and type. Compare it with a cup, 
 Creating a JavaScript Object
 Example 1 :
 const person = {firstName:"John", lastName:"Doe", age:50 };
 person.firstName + " is " + person.age + " years old.";
 Result :
 'John is 50 years old.'
 Spaces and line breaks are not important. An object definition can span multiple lines:

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 string : String is a primitive data type in JavaScript. A string is textual content. 
          It must be enclosed in single or double quotation marks.
          Since, string is character index, it can be accessed using for loop and for-of loop.
 ( A JavaScript string is zero or more characters written inside quotes. )
 Example
 var name = "Ganesh";
 Result :
 "Ganesh"

 String Length : To find the length of a string, use the built-in length property

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ARRAY : An array is a special variable, which can hold more than one value at a time.
Creating an Array
Using an array literal is the easiest way to create a JavaScript Array.

Syntax:
const array_name = [item1, item2, ...];
Example 
const bikes = ["PULSAR", "ACTIVA", "PLEASURE"];

Using the JavaScript Keyword new

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                                   React Native FlexBox
Flexbox : Flexbox works the same way in React Native as it does in CSS on the web, with a few exceptions.
           The defaults are different, with flexDirection defaulting to column instead of row, alignContent
           defaulting to flex-start instead of stretch, flexShrink defaulting to 0 instead of 1, 
           the flex parameter only supporting a single number.
       Name                         Type
1 flexDirection                 row , row-reverse , column , column-reverse .
2 alignItems                    flex-start , flex-end , center , stretch , baseline .
3 justifyContent                flex-start , flex-end , center , space-between , space-around.
4 alignSelf                     auto , flex-start , flex-end , center , stretch , baseline .