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  • write a program to print n number from 1 to n in nth seconds
this would perfectly finefunction x() {  for (let i = 1; i < 6; i++) {    setTimeout(() => {      console.log(i);    }, i * 1000);  }}x();

but while using var it won't work

function x() {  for (var i = 1; i < 6; i++) {    setTimeout(() => {      console.log(i);    }, i * 1000);  }}x();

here the settimeout will make a copy of function and store it . in the referance of the var i .

  • let has a block scope , it is a new copy of all let is created each time it is called it is creating a sperate copy of itself. or i is refering to a new memory location.

let is block scope ..

how to do it without var ?

function x() {  for (var i = 1; i < 6; i++) {    function close(i) {      setTimeout(() => {        console.log(i);      }, i * 1000);    }    close(i);  }}x();

now it will create a new copy of i itslef :)

example of closure

function outer(){   var a = 10;    function inner(){     console.log(a);    }    return inner;}
//what are these for?outer()();
//another way to do itvar close = outer();close();

()() call the inner function :)

  • how this will behave with argument ?
the parameter will form closer with the parameter as well :)

disadvange ??

it can consume a lot of meomory as it is not garbage collected till the program expire.

if not handled properly it can lead to meomory leak.

grabage collector

in browser/engine the garbage collector will free the untilize space in the memory.

whever their is un used variable it will free up the meomory.

Relation b/w garbage collector and function ?

function a() {  var x = 0;  return function b() {    console.log(x);  };}var y = a();