Javascript mongoDB takes variable name rather than value of the variable

Question

I am using mongoDB with javascript. I am updating an item in a collection using the following function and passing in "server_name" as the variable attribute_name:

    async update_server_attribute(db, server_id, attribute_name, new_value){
        var my_query = { "server_id": server_id }
        var updated_val = { $set: {attribute_name: new_value } }
        db.collection("servers").updateOne(my_query, updated_val)
    },

I would expect the dict to update to the following:

{"server_name" : new_val}

Instead it does the following:

{"server_name" : old_value, "attribute_name" : new_val}

Can anyone explain this strange behavior and how to fix it?

Answer 1

In JavaScript, {attribute_name: new_value } is treated the same as {"attribute_name": new_value } . To have JavaScript use the value of attribute_name as the key, use computed property name syntax by surrounding it with square brackets:

var updated_val = { $set: {[attribute_name]: new_value } }