Align selected object to object "A" (XYZ) and then to object "B" (Y)

Hello! basically I have a dummy object "X" and 2 geometry objects "A" and "B".

I need to align the selected Dummy "X" firstly to "A" on all of its axes, and then to "B" only on its Y axis.

I have found the following line which aligns the selected object to all axes XYZ (oddly it squashes the Dummy's bounding box)

$.transform = (getNodeByName "A").transform

$.transform = (getNodeByName "B").transform

and what I need is for the second line of code to constrain the transform operation to the Y axis.

The normal way of doing this is by using the ALIGN tool twice (first on A and then on B disabling X and Z), but I need to automate this. Any help is highly appreciated!