Answers for "const vs let vs var javascript"

26

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.
Posted by: Guest on May-11-2021
0

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.
Posted by: Guest on February-12-2021
0

difference between var and let and const in javascript

var variable1 // declared using var
const variable2 // declared using const

myFunction1();

function myFunction1() {
  variable1 = "hello!";
  console.log(variable1);
  // "hello!"
}

myFunction2();

function myFunction2() {
  variable2 = "hello!";
  // error: variable2 is a constant and can not be redifined
}

myFunction3(true);

myFunction3(codition) {
  if(condition) {
    let variable3 = "helo!" // declared using const
  }
  variable3 = "hello!";
  // error: variable3 is out of scope
}

/*

Therefore, 
  
  var:
    -can be declared outside any function to be used inside any function
    -can be declared inside any function or any other {} which are of only if or if-else or switch etc. and can be used anywhere inside the function
    -can be changed again and again anywhere
  let:
    -can be declared outside any function to be used inside any function
    -if declared inside any function or any other {} which are of only if or if-else or switch etc. and can't be used anywhere inside the function and can be only used inside statement
    - can be changed again and again only inside the statement in which they are made in
    const:
    -can be declared outside any function to be used inside any function
    -can be declared inside any function or any other {} which are of only if or if-else or switch etc. and can be used anywhere inside the function
    -cannot be changed again and agan anywhere, if tried to, will result in an error

*/
Posted by: Guest on July-23-2021

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