Why are the properties of this object undefined? Javascript

Attribute is an object in this form:

   var attribute = {
    AttributeId: attributeId,
    EntityId: entityId,
    AttributeDBName: attributeDbName,
    AttributeDisplayName: attributeDisplayName,
    IsSearchable: isSearchable,
    IsDeleted: isDeleted,
    IsVisible: isVisible,
    AttributeTypeId: attributeTypeId,
    Description: description,
    IsSystem: isSystem,
    IsActive: isActive,
    IsUnique: isUnique,
    IsRequired: isRequired,
    IsPersistent: isPersistent,
    DefaultValue: defaultValue
};

That attribute then gets passed to this function along with the ID of a grid:

function AddAttributeToGrid(attribute, gridId) {

    console.log(attribute); //Works! Displays the attribute.

    var id = a.attributeId;

    console.log(id);//UNDEFINED? WHAT?   

}

If I create a global variable (let's call it 'tempAttribute') and set it inside of AddAttributeToGrid, like so:

 function AddAttributeToGrid(attribute, gridId) {
    tempAttribute = attribute
}

I can then access the properties of tempAttribute...

Why can I not get the data from the properties? What is going on?