Basic Types and Values

Primitive Types

1. Number Type

   // Number Representation
   let integer = 42;           // Whole number
   let decimal = 3.14;         // Floating-point number
   let scientific = 5e3;       // Scientific notation (5000)
   let hexadecimal = 0xFF;     // Hexadecimal (255)
   let binary = 0b1010;        // Binary representation (10)
   

   • Range from -(2^53 - 1) to (2^53 - 1)
   • Special values: Infinity, Infinity, NaN
   • NaN is a unique value meaning "Not a Number"
   • NaN is the only JavaScript value that is not equal to itself
   • Number.MAX_SAFE_INTEGER and Number.MIN_SAFE_INTEGER define safe integer ranges

2. String Type

   // String Immutability Demonstration
   let str = "immutable";
   str[0] = 'I';  // This won't change the string
   

   • Immutable: Strings cannot be changed, only replaced
   • Unicode support
   • Template literals allow multi-line strings and expression interpolation

3. Boolean Type

   Similar to boolean in any programming language, it has two values true and false

   All values except false, 0, 0n, -0, “”, null, undefined, and NaN are truthy values.

4. Undefined Type

   let string;
   console.log(string); // undefined
   

   undefined represents a variable that has been declared but not assigned a value, automatically set by JavaScript. It is diffrent from null.

5. Null Type

   null is a special value in JavaScript that developers deliberately use to show a variable is intentionally empty or has no value assigned to it.

   • typeof null returns "object" (a historical bug in JavaScript)

6. Symbol Type ( ES6 ) In JavaScript, a Symbol is a unique and immutable primitive type that creates guaranteed distinct values, primarily used to create non-string property keys and prevent property name collisions in objects

   // guaranteed distinct values
   let sym1 = Symbol("description");
   let sym2 = Symbol("description");
   console.log(sym1 === sym2); // false
   
   // use case in objects to get unique keys
   const uniqueKey = Symbol('description');
   const obj = {
       [uniqueKey]: 'This is a unique property'
   };
   

7. BigInt Type ( ES2020 )

   let bigNum = 1234567890123456789012345678901234567890n;
   let bigIntValue = BigInt(42);
   

   • Represents integers larger than 2^53 - 1
   • Denoted by 'n' suffix or BigInt() constructor
   • Cannot be mixed with regular numbers in operations

Type checking and coercion

Type of operator

The typeof operator we discussed earlier is used for type checking in JavaScript. It allows you to determine the type of a given variable

Type Coercion

Type Coercion in JavaScript is the process of converting one data type to another, either automatically (implicit) or manually (explicit).

Type conversion methods are explicit ways to convert a value from one type to another. Some common methods include:

• String() – Converts a value to a string.
• Number() – Converts a value to a number.