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Data Types and Literal in JavaScript

JavaScript support four primitive types of values and supports complex types such as objects and arrays. Primitive type are types that can be assigned a single literal value such as number, string or boolean value. Literal are fixed values, which literally provide a value in a program.

The Primitive data type are:

1. Number :
Consists of integer and floating point numbers and a special NaN (not a number) value.
Integer Literals can be represented in JavaScript in decimal, hexadecimal, and octal form .
Floating-point literals are used to represent numbers that require the use of a decimal point, or very large or very small numbers that must be written using exponential notation. A floating-point number must consist of either a number containing a decimal point or an integer followed by an exponent.
Eg : 22, 15.20, -36.7, 2E5, 0x6F

2. Boolean :
Java Script supports a pure boolean type that consists of two values true and false.
Logical operators can be used in Boolean expressions.
Java Script converts the boolean values true and false into 1 and 0 when they are used in numerical expressions.

3. String :
consists of string values that are enclosed in double or single quotes.
Java Script provides built-in support for strings. A string is a sequence of Zero or more characters that are enclosed by double(") or single (') quotes. If a string begins with a double it must end-with a double quote. If a string begins with a single quote it must end with a single quote.
Eg : "james", '2, USA'

4. Null :
Null value is common to all JavaScript types. It is used to set a variable to an initial value that is different from other valid values. Use of the null value prevents the sort of errors that results from using uninitialized variables. Null value is automatically converted to default values of other types when used in an expression.

5. Type Casting :
In Java Script variables are loosely cast. The type of a Java Script variable is implicitly based on the literal values that are assigned to it from time to time.
For instance, combining the string literal " Total amount is " with the integer literal 1000 results in a string with the value "total amount is 1000" . Adding together the literal 10.5 and the string "20" results in the floating point integer literal 30.5. This process is known as type casting.

Casting Variables
In other to make working with data types convenient, variables are created . In Java Script variables can be created that can hold any type of data.
Declaring a variable tells JavaScript that a variable of a given name exists so that the Java Script interpreter can understand references to that variable name throughout the rest of the script.
Although it is possible to declare variables by simply using them, declaring variables helps to ensure that programs are well organized and helps keep track of the scope of the variables. Variables can be declared using var command.
Syntax

var <variable name:> = value ;

Example :
var first_name;
var last_name="jacob";

The equal sign (=) used in assigning a value to variable is known as an assignment operator.
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