Hairbrush

FIG. 1 is a front perspective view of a hairbrush, showing my new design; FIG. 2 is a rear perspective view thereof; FIG. 3 is a front view thereof; FIG. 4 is a rear view thereof; FIG. 5 is a left side view thereof; FIG. 6 is a right side view thereof; FIG. 7 is an enlarged top plan view; FIG. 8 is an enlarged bottom plan view; and, FIG. 9 is an enlarged detail view of area 9 in FIG. 1 . The dot-dash broken lines shown in the drawings are for depicting enlarged view indicators, and form no part of the claimed design.