I have this code 

```
var a = ['a', 'b', 'c'];
var b = ['a', 'd', 'b', 'c'];

for (var i = 0; i < a.length; i ++) {
if (a[i] === b[i]) {
alert('ok');
  }
}

```

How could I skip in array `b` the `'d'` element, so it alerts me always Ok?

UPDATED

I just want to know how skip certain index. I mean if I don't want to look at index `0` I write for `(var i = 1; i < a.length; i ++)`, if I don't want to check last index, I do `a.length-1`, but how I skip index, if it is not first/last?