Jesus Christ crucifixion in Islam?

I was just wondering, I'm a new Muslim convert, and I was talking with one of my friends who is also Muslim and he told me that Jesus did not get crucified, but it was made to seem that way and Allah switched his soul with one of his traitors and ascended him to Heaven. I'm just curios to know, when exactly did Jesus ascend to Heaven? Right when he was about to get crucified or before he was put to the cross?