findByIdAndUpdate With Multiple Subdocuments - node.js

Question

So I'm working with NodeJS and MongoDB, and I'm making an endpoint that lets clients update their user profiles with several optional data fields. So, one of the update queries can look like this:
{
name: { givenName: 'first' },
about: 'whatever',
auth: { password: 'hashedPW' }
}
The Mongoose API docs state the following info about findByIdAndUpdate: All top level update keys which are not atomic operation names are treated as set operations.
So the top level key, about, works fine to update. However, the nested keys, name and auth are overwritten by the update values, rather than just having the values set.
Now I could go through and manually change each of the fields to be a $set key, but there are a lot of different fields, so to do this would be pretty annoying. Is there an easy way to apply the $set rule to the subdocuments as well? i.e. transform the statement into this, with a Mongoose option or something:
{
$set : { name: { givenName: 'first' } },
$set : { about: 'whatever' },
$set : { auth: { password: 'hashedPW' } }
}

Answer 1

You basically need to tranform your input object into "dot notation" form in order to avoid overwring other possible sub-keys in your update. This is quite simple really:
var obj = {
name: { givenName: 'first' },
about: 'whatever',
auth: { password: 'hashedPW' }
};
var target = {};
function dotNotate(obj,prefix) {
prefix = (typeof(prefix) === 'undefined') ? "" : prefix;
Object.keys(obj).forEach(function(key) {
if ( typeof(obj[key]) === "object" ) {
dotNotate(obj[key],key + ".")
} else {
target[prefix + key] = obj[key];
}
});
}
dotNotate(obj);
Now the target object looks like this:
{
"name.givenName" : "first",
"about" : "whatever",
"auth.password" : "hashedPW"
}
So the update block of your statement is merely written as:
{ "$set": target }
For reference, the dotNotate() function can be a bit more refined and self contained. Also including shorter default assignments as valid input would generally be considered be "truthy". Also the "prefix" should have been pre-pended on each call to make this work at arbitrary depth:
function dotNotate(obj,target,prefix) {
target = target || {},
prefix = prefix || "";
Object.keys(obj).forEach(function(key) {
if ( typeof(obj[key]) === "object" ) {
dotNotate(obj[key],target,prefix + key + ".");
} else {
return target[prefix + key] = obj[key];
}
});
return target;
}
Then you can use either inline:
var update = { "$set": dotNotate(obj) };
Or pass in a defined object like this if you prefer:
var update = { "$set": {} };
dotNotate(obj,update["$set"]);
With the same results.
Also fine for arrays and nested depth:
{
"things" : [
{
"a" : 1,
"b" : 2
},
{
"a" : 3,
"b" : 4
}
],
"bool" : false
}
With output:
{
"things.0.a" : 1,
"things.0.b" : 2,
"things.1.a" : 3,
"things.1.b" : 4,
"bool" : false
}