  We explore the effects of strangeness and $\Delta$ resonance in baryonic
matter and compact stars within the relativistic-mean-field (RMF) models. The
covariant density functional PKDD is adopted for $N$-$N$ interaction,
parameters fixed based on finite hypernuclei and neutron stars are taken for
the hyperon-meson couplings, and the universal baryon-meson coupling scheme is
adopted for the $\Delta$-meson couplings. In light of the recent observations
of GW170817 with the dimensionless combined tidal deformability $197 \leq
\bar{\Lambda}\leq 720$, we find it is essential to include the $\Delta$
resonances in compact stars, and small $\Delta$-$\rho$ coupling $g_{\rho
\Delta}$ is favored if the mass $2.27{}_{-0.15}^{+0.17}\ M_\odot$ of PSR
J2215+5135 is confirmed.
