const rockets = [ { country:'Russia', launches:32 }, { country:'US', launches:23 }, { country:'China', launches:16 }, { country:'Europe(ESA)', launches:7 }, { country:'India', launches:4 }, { country:'Japan', launches:3 } ]; const launchOptimistic = rockets.map(function(elem) { return { country: elem.country, launches: elem.launches+10, } }); console.log(launchOptimistic);