Joy is the same as happiness in the Old Testament. But in the New Testament joy is not based on circumstances but based on being close to God. It's a fruit of the Spirit.
(Galatians 5:22-23 NIV) But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, {23} gentleness and self-control. Against such things there is no law.
RE: Joy Is Central In The Christian Faith If Christ Is At The Center Of Our Lives