Specified in the REPL options, this is a flag that specifies whether the default eval function should execute all JavaScript commands in strict mode or default (sloppy) mode. Possible values are:
repl.REPL_MODE_SLOPPY- evaluates expressions in sloppy mode.repl.REPL_MODE_STRICT- evaluates expressions in strict mode. This is equivalent to prefacing every repl statement with'use strict'.