Object Assign

let item = {
    id: 123,
    name: "JavaScript Tutorial",
    price: 500,
    author: "John Doe"
}

let category = {
    category_id: 1,
    category_name: "Tutorials"
}

let shop = Object.assign(item, category);

console.log(shop);

//Result: 

/*
    {
        id: 123,
        name: "JavaScript Tutorial",
        price: 500,
        author: "John Doe",
        category_id: 1,
        category_name: "Tutorials"
    }

*/