рони,
var features = [{
type: "Coupe",
modification: ["325", "328", "330", "M"],
errors : 0
}, {
type: "Cabrio",
models: ["3-series", "6-series", "Z-series"],
errors: 0
}];
var arr = features.forEach( function( item ){
features.keys( item )
})
console.log( features.keys( item ) ) выводит
ArrayIterator {}
ArrayIterator {}