setTimeout in for-loop does not print consecutive values [duplicate]

Answer 1

This's Because!

1. The timeout function callbacks are all running well after the completion of the loop. In fact, as timers go, even if it was setTimeout(.., 0) on each iteration, all those function callbacks would still run strictly after the completion of the loop, that's why 3 was reflected!
2. all two of those functions, though they are defined separately in each loop iteration, are closed over the same shared global scope, which has, in fact, only one i in it.

the Solution's declaring a single scope for each iteration by using a self-function executed(anonymous one or better IIFE) and having a copy of i in it, like this:

for (var i = 1; i <= 2; i++) {

     (function(){

         var j = i;
         setTimeout(function() { console.log(j) }, 100);

     })();

}

the cleaner one would be

for (var i = 1; i <= 2; i++) {

     (function(i){ 

         setTimeout(function() { console.log(i) }, 100);

     })(i);

}

The use of an IIFE(self-executed function) inside each iteration created a new scope for each iteration, which gave our timeout function callbacks the opportunity to close over a new scope for each iteration, one which had a variable with the right per-iteration value in it for us to access.