let var const difference javascript code example

Example 1: var let const javascript

Const vs Let vs Var

const pi = 3.14

pi = 1 
cannot do this becuase with const you cannot change the value

_____________________________________


Let --> is block level 

for(let i = 0; i < 3; i++) {
console.log(i) --> it will console here
}
console.log(i) ---> Not here


---------------------------------------

Var is for variables available to the entire function 


for(var j = 0; j < 3; j++) {
console.log(j) --> it will console here
}
console.log(j) ---> it will console here

Example 2: 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.

Example 3: let and var difference

function run() {
  var foo = "Foo";
  let bar = "Bar";

  console.log(foo, bar);

  {
    let baz = "Bazz";
    console.log(baz);
  }

  console.log(baz); // ReferenceError
}

run();

Example 4: 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.

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