Answers for "const vs var vs let 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.

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.

let vs var vs const

// ⚡ Initialization
var a; //✅
let b; //✅
const c; //❌ const must have an initial value

// ⚡ Re-Assignment
var d = 1; 
d = 10; //✅

let e = 2; 
e = 20; //✅

const f = 3; 
f = 30 //❌ const value is always constant and cannot be reassigned

// ⚡ Re-Declaration
var g = 1; 
var g = 10; //✅

let h = 2; 
let h = 20; //❌ must use variable name only to reassign, cannot be reassigned 

const i = 3; 
const i = 30 //❌ cannot be reassigned

// ⚡ Scope [Global, Function or local and block scope]
// Global Scope ==> Any variable that is declared outside any of the function
// Function Scope(var) ==> Can be accessed inside the function it was declared and its child
// Block Scope(let and const) ==> Con be accessed inside curly brackets where it was declared and its child

function myFunction(){
    var myName1 = 'Asmita';
    let myName2 = 'Dikshit';
    const myName3 = 'Sizen';
    console.log(myName1);
    console.log(myName2);
    console.log(myName3);

    if(true){
        console.log(myName1);
        console.log(myName2);
        console.log(myName3);

        var myAge1 = 13;
        let myAge2 = 15;
        const myAge3 = 14;
        console.log(myAge1);
        console.log(myAge2);
        console.log(myAge3);
    }

    console.log(myName1);
    console.log(myName2);
    console.log(myName3);

    console.log(myAge1);
    console.log(myAge2);
    console.log(myAge3);
};
myFunction();

difference between var let and const in javascript with example

//functional scope 
 var a; // declaration
 a=10; // initialization; 
//global scope
// re-initialization possible
 let a;//only blocked scope & re-initialization possible
 a=10;
let a =20;
if(true){
  let b =30;
}
console.log(b); // b is not defined
const // const also blocked scope,Re-initialization and re-declaration not possible
const a; // throws error {when we declaring the value we should assign the value.
const a =20;
if(true){
  const b =30;
}
console.log(b); // b is not defined
console.log(a); // no output here because code execution break at leve b.

var or const in javascript

// var declares a variable, meaning its value will vary. 
// const declares a constant, meaning its value will remain 
// consistant and not change. 
// If your variable changes throughout the program or website, 
// declare it using a var statement. 
// Otherwise, if its value does not change, declare it using 
// a const statement. 

const myConst='A const does not change.';

var myVar='A var does change.';

var myVar=2;

what is the different between var and let and const in js

var tester = "hey hi";
    
    function newFunction() {
        var hello = "hello";
    }
    console.log(hello); // error: hell
o is not defined