Question: I am trying to do something like this

```
var teller = 1;
if (teller % 2 === 0) {
  "do this"
} else {
  "do something else"
}
teller++;

```

The problem is that he always comes into the else loop.
Someone knows why?

Answer: 
because `1 % 2 === 0` returns `false`

you might want to put it inside a loop

```
var teller = 1;
while(teller < 100){ //100 is the range, just a sample
    if (teller % 2 === 0) {
         "do this"
    } else {
          "do something else"
    }
    teller++;
}

```
Stepping through your code:

```
var teller = 1;          //teller is now 1
if (teller % 2 === 0) {  //1 % 2 === 1, so this statement is skipped
  "do this"
} else {                 //since the if statement was skipped, this gets run
  "do something else"
}
teller++;                //this has no affect on the above

```

If you want to put this in a loop, see @DryrandzFamador's answer.