My whatever it is is very small, so I just Googled Dwarf Malus x Crabapple. My bush/tree doesn't resemble the pictures on Google. Pictures show crab apple trees with one trunk. Mine has multiple trunks (if that's what they are called).
Also Googled Philadelphus lewisii 'Blizzard' and Exochorda. Those look really full when in bloom. Mine did not look that full. Maybe because it could be newer?
, leaves alternate.
Here are some more pictures.