Update meteor mongo collection

i want to update a mongo collection using meteor without using _id , as i want to use update query where my userId (defined by myself) value is specific as given but when i update using as it work for me

iphysiousers.update(_id,{
$set:{

}

}

but when i use as it not update my data so my question is only that how i can update using my custom id field

iphysiousers.update(userId,{
$set:{

}

}

You don’t have to pass the ID. You can pass a mongo selector instead to select the document(s) to update. Check the docs for collection update.