Chlorine reacts with sodium hydroxide under various condition to give 

$\underset{\text{ (dil.) }}{2\mathrm{NaOH}+{\mathrm{Cl}}_2}\stackrel{\mathrm{Cold}}{\to }\mathrm{NaCl}+\underset{\text{ Sod. hypochlorite }}{\mathrm{NaClO}}+{\mathrm{H}}_2\mathrm{O}$

$\underset{\text{ (conc.) }}{6\mathrm{NaOH}}+3{\mathrm{Cl}}_2\stackrel{\mathrm{heat}}{\to }5\mathrm{NaCl}+\underset{\text{ Sodium chlorate }}{{\mathrm{NaClO}}_3}+3{\mathrm{H}}_2\mathrm{O}$