if statement is not working properly for account types

I am creating a platform for buyers and sellers. I want to differentiate between a buyer's account and a seller account so I tagged each account as user or seller. The firebase database structure is like this,

I want to do a check if the current user is a "user" or "seller" using this function

function checkaccttype(){


firebase.auth().onAuthStateChanged((user) => {
    if (user) {

        var userId = firebase.auth().currentUser.uid;
        var userref = rootref.ref('/Users/' + userId).once('value', function(snapshot) {

            console.log(" let's check if this guy is a seller")

            if (snapshot.val().accttype = "seller") {
                // window.location = "../html/SellerDB.html"

                remove("seller_btn");

                console.log("this guy is a seller")
            } else {
                console.log(" common this guy is no SELLER, is a user")
            } 


        })


    } else {
        console.log("user is not logged in");
    }

})

}

but surprisingly, event if the accttype = "user", it still recognize it as a seller by printing this "this guy is a seller". How can I properly differentiate the two different accounts in firebase?