Reduce with deconstruction or forEach - Iteration and Airbnb JavaScript Style Guide

Just use a dead simple loop: function alwaysBlue(things) { const blueThings = {} for (const key in things) // or `for (const key of Object.keys(things))` blueThings[key] = 'blue' return blueThings } Those iteration methods are only good for arrays, which we aren't dealing with here.