I really liked this article. I just got a point that in the section 08 the good example have a simple error. That code: const { add, subtract } = require ( './calculations' ) add( 4 , 2 ); calculate.subtract( 4 , 2 ); should be: const { add, subtract } = require ( './calculations' ) add( 4 , 2 ); subtract( 4 , 2 );