JavaScript 4 🧬 Variables

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### a - JavaScript variable declaration 1 of 2
* variables JavaScript are used to store and manage data
* Those data can be manipulated or accessed through the code execution
* They act as containers for values
* They allow you to refer back to these values by their assigned name
* You can declare and initialize their value at the same time
* JavaScript has 3 kinds of declaration
* var → The oldest way to declare variable. Variables declared with var have function scope or global scope.
* They are also hoisted, which means that they are moved to the top of the containing scope during execution

### b - JavaScript variable declaration 2 of 2
* let → allows block-scoped variables. Variables accessible only within the block, statement or expression where they are defined. Introduced in ES6
* const → is used to declare constants which are variables that cannot be reassigned after their initial assignment. Introduced in ES6
* constants must be initialized at the time of declaration
* const also declares block-scoped local variables
* Variables can only contain letter (both uppercase and lowercase), digits, underscores (`_`), and dollar signs (`$`)
* Variables cannot start with a digit
* JavaScript is case-sensitive, so `myVar`, `MyVar`, and `MYVAR` are considered different variables.

### c - JavaScript types of Data
* variables in JavaScript can hold various types of data, primitive and reference type
* Primitive Types: Boolean → true or false
* String → 'hello world' Number → 1978
* undefined → variable's value is not defined * null → it donates a null value
* BigInt → 124312435423543645n Symbol → its instances are unique and immutable
* Reference Types: Object → Collections of key-value pairs
* Array → lists of values used for storing multiple items under a single variable name
* Function → Reusable blocks of code that perform specific tasks, accepting inputs and optionally returning outputs.

### d - JavaScript Variable Scope
* JavaScript variables can belong to 1 of the 3 following scopes:
* Global Scope → Variables declared outside any function or block are global
* They are accessible throughout the entire script.
* Function Scope → Variables declared inside a function
* They are only accessible within that function.
* Block Scope → Variables declared inside a block `{` `}`
* They are only accessible within that block.
* Such blocks are switch statement, try...catch statement, for statement, function body and static initiliaztion block

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