JAVASCRIPT

var vs let vs const

var: 
	- hoisted (always declared at top of scope, global if none)
    - function scope
let:
    - block scope
    - not redeclarable
const: 
    - block scope
    - not reassignable
    - not redeclarable
    
Note: Although it may seem like these hold only semantic meaning, using the
appropriate keywords helps the JS engines' compiler to decide on what to optimize.

let vs const

`const` is a signal that the identifier won't be reassigned.

`let` is a signal that the variable may be reassigned, such as a counter in a
loop, or a value swap in an algorithm.

It also signals that the variable will be used only in the block it's defined
in, which is not always the entire containing function.

what is the difference between let and const in javascript

The difference is that with const you can only only assign a value to a variable
once, but with let it allows you to reassign after it has been assigned.

js var vs let

let = 10 // accessable only in defined scope
var = 10 // accessable in the function it is declared in (global variable in a function)
  

difference between var, let, const

// var is a function scope ***
if(true){
    var varVariable = 'This is var';
    var varVariable = 'This is var again';
}

console.log(varVariable); // This is var again

// let is a block scope ***
if(true){
    let letVariable = 'This is let';
    let letVariable = 'This is let again';

    // let variable can't re-define but we can re-assign value


    console.log(letVariable); // let letVariable = 'This is let again';^SyntaxError: Identifier 'letVariable' has already been declared
}

console.log(letVariable); //ReferenceError: letVariable is not defined



// const variable can't re-define and re-assign value
// const is a block scope ***
if(true){
    const constVarible = {
        name: 'JavaScript',
        age: '25 years',
    };
    constVarible.name = 'JS';

    console.log(constVarible) // {name: 'JS',age: '25 years'} <= we can update const variable declared object 
}