  On the basis of two requirements: the avoidance of the curvature singularity
and the Maxwell theory as the weak field limit of the nonlinear
electrodynamics, we find two restricted conditions on the metric function of
$(2+1)$-dimensional regular black hole in general relativity coupled with
nonlinear electrodynamics sources. By the use of the two conditions, we obtain
a general approach to construct $(2+1)$-dimensional regular black holes. In
this manner, we construct four $(2+1)$-dimensional regular black holes as
examples. We also study the thermodynamic properties of the regular black holes
and verify the first law of black hole thermodynamics.
