Current is a vector or scalar?

Yes it is Scalar, because Current is defined to be the quantity of charge that flows from a point in a wire per unit time. In many cases the direction of the charge flow changes from one point to another, but the amount of charge passing a given point in a wire is the same at all points. So it is a scalar, but  obviously you may get doubt that if it is scalar, why we perform vector addtion of currents in case of transformer and other A.C circuits. To make it clear we should know the concept of PHASOR i.e., to represent Sinusoidally varying quantity we use phasor. Therefore, to add two phases displaced by some angle we must use vector addition rather we should call it as phasor addition thats why in AC phasor diagrams are more popular.