Run this code

for (var i=1; i<=5; i++) {
	setTimeout( function timer(){
		console.log( i );
	}, i*1000 );
}

What you expected

1
2
3
4
5

But, result is

6
6
6
6
6

Solution is

for (var i = 1; i <= 5; i++) {
    setTimeout((function timer(j) {
        return function() {
            console.log(j);
        }
    })(i), i * 1000);
}

or

for (var i=1; i<=5; i++) {
	(function(j){
		setTimeout( function timer(){
			console.log( j );
		}, j*1000 );
	})(i);
}