Let's say I have two nested objects that are structured very similarly:

let obj = {
    "fontFamily": {
        "primary": {
            "sans": "Roboto"
        }
    }
}

let obj2 = {
    "fontFamily": {
        "primary": {
            "mono": "Roboto Mono"
        }
    }
}

How can I merge them into one nested object like the below?

{
    "fontFamily": {
        "primary": {
            "sans": "Roboto",
            "mono": "Roboto Mono"
        }
    }
}