Alexander Belov,
var features = [{
type: "Coupe",
modification: ["325", "328", "330", "M"],
errors : 0
}, {
type: "Cabrio",
models: ["3-series", "6-series", "Z-series"],
errors: 0
}];
features.forEach( function( item ){
item.individual = null;
})
alert(JSON.stringify(features))