Topics

#token

1. 1. It is the smallest unit of programming language.
2. 2. We have 5 types of operators,punctuators,keywords ,identifiers , literals.

#Operators

1. 1. These are symbols or words that represent mathematical, logical, or other operations.
2. 2. Examples include : +, -, *, /, =, ==, ===, &&, ||, !, and typeof.

#Punctuators

1. 1. These are symbols used to group, separate, or punctuate code.
2. 2. Examples include parentheses (), curly braces {}, square brackets [], commas ,, semicolons ;, and the period . (used to access object properties).

#keywords

1. 1. These are reserved words that have a special meaning in the language.
2. 2. Examples like if, else, for, while, function, and return,etc.

#identifiers

1. 1. These are user given names to variables, functions, and other objects in the code.
2. 2. Identifier name can not start with number.
3. 3. Identifier name should not be a keyword
4. 4. If Identifier is of multiple word, instead of using space, we have to use underscore.
5. 5. identifier name should not have special character but can start with underscore(_) and dollar($).

#literals

1. 1. These are values used in our program like number(2),string('hello world') , etc.

#Types of literals / Datatypes

1. 1. Primitive
2. 2. Non-Primitive

#Primitive literals

1. 1. In JavaScript, a primitive data type is a data type that represents a single value.
2. 2. JavaScript treats primitive values as immutable values, means that their value cannot be changed. Instead, when you perform an operation that appears to modify a primitive value, you are actually creating a new object with new value and assigning it to a variable. Here , variable will hold the reference of latest object with new value and the previous object with it's value will garbage collected.
3. 3. We have 8 primitive types of literals -number , bigint , boolean , nan , undefined , null , symbol , string..

#Primitive datatypes

1. 1. Number

   • 1. This data type represents a numeric value. It can store both integers and floating-point values.
   • 2. It's range is from -2⁵³-1 to 2 ⁵³-1 .

2. 2. BigInt

   • 1. It is used to represent integers that are larger than the Number data type
   • 2. It's range is more than -2⁵³-1 and more than 2⁵³-1 .
   • 3. To represent the given integer as bigint , we have to suffix 'n' after the integer.
     Example : 10 is number type and 10n is bigint type.

3. 3. Boolean

   • 1. This datatype represents a logical entity and can only have two values: true or false.

4. 4. Null

   • 1. This datatype represents a null or empty value.
   • 2. It is used to mark the memory block empty intentionally.

5. 5. Undefined

   • 1. This datatype represents an uninitialized value.
   • 2. When memory block is unintialized , js engine implicitly initialize that memory block with 'undefined' in variable phase.
   • 3. For variable declared with 'var' it will initialize it in variable phase
   • 4. For variable declared with 'let' and 'const' it will not initialize it in variable phase.

6. 6. NaN

   • 1. It stands for 'not a number'.
   • 2. It represents computational error.
   • 3. When js engine is not able compute result it returns 'NaN'.
   • 4. Example : "Hello" + 1 = Hello1 and "Hello" - 1 = NaN
     In first case , js engine concatnated the string with number.
     In second case , js engine is able to compute anything because we can not subtract 1 from "Hello" string therefore it returns NaN.

7. 7. Symbol

   • 1. It represents a unique identifier.
   • 2. We have Symbol function which is used to generate unique idenitifiers in our program.

8. 8. String

   • 1. It represents collection of characters.
   • 2. We have two types of strings :- single line and multi line string.
     
   • 3. Single line string :
     - It is enclosed by single quotes (' ') and double quotes (" ") .
     - It doesnot allow line breaks and whitespaces.
   • 4. Multi line string :
     - It is enclosed by backticks (` `).
     - It allow line breaks and whitespaces.
     - It is also called as template string.
     - Template strings allow us to insert variables and expressions directly in the string using ` ${ variable_name } ` notation.

#Non-Primitive literals

1. 1. In JavaScript, a non primitive data type is a data type that represents multi value.
2. 2. JavaScript treats non-primitive values as mutable values, means that their value can be changed. When we try to update a value , new object is not created . Here value is changed in the same memory block.
3. 3. Non-primitive datatype : object ,array , etc