Cloud Firestore: Update fields in nested objects with dynamic key

Question

following the official documentation of firestore :

{
    name: "Frank",
    favorites: { food: "Pizza", color: "Blue", subject: "recess" },
    age: 12
}

// To update favorite color:
db.collection("users").doc("frank").update({
    "favorites.color": "Red"
})

I would like to use a dynamic key instead of color.

db.collection("users").doc("frank").update({
    "favorites[" + KEY + "].color": true
});

this is of course not possible and will throw an error.

I've been trying to do this :

db.collection("users").doc("frank").update({
    favorites: {
        [key]: {
            color": true
        }
    }
});

It is actually updating with the right key but unfortunately, it is overwriting the other keys (they are being deleted).

Brieuc · Accepted Answer · 2017-11-14 22:16:06Z

118

I found the solution inspired by a firebase solution (replacing "/" by ".").

var usersUpdate = {};
usersUpdate[`favorites.${key}.color`] = true;

db.collection("users").doc("frank").update(usersUpdate);

answered Nov 14, 2017 at 22:16

Brieuc

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8 Comments

Kushagra Gour Over a year ago

Related doc -> firebase.google.com/docs/firestore/manage-data/…

user9315861 Over a year ago

I'm wondering if that actually works. I would expect it to overwrite the current value of usersUpdate with the new one with a single value, namely {favorites {KEY: {color: true}}}.If what you say is correct, then there would be no way to actually update usersUpdate to a completely new value.

Nth.gol Over a year ago

more briefly, @Georg Hackenberg points out this solution: db.collection('users').doc('frank').update({ [`favorites.${key}.color`] = true })

Brieuc Over a year ago

Why is it invalid? You can use backticks in es6. This solution still work, it is really similar to the answer below. developers.google.com/web/updates/2015/01/ES6-Template-Strings

Sachin Rathod Over a year ago

This solution is wrong as this will create a new field usersUpdate of type map with child favorites.${key}.color : true - if key=1234 then usersUpdate field will look like

usersUpdate                                                                                        {                                                                         favorites.1234.color : true                                                    }

|

Georg Hackenberg · Accepted Answer · 2021-09-29 09:26:19Z

77

This solution worked for me:

db.collection('users').doc('frank').update({
  [`favorites.${key}.color`]: true
});

edited Sep 29, 2021 at 9:26

answered May 7, 2018 at 19:54

Georg Hackenberg

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6 Comments

Fernando Rojo Over a year ago

Correct solution.

coolcool1994 Over a year ago

db.collection('users').doc('frank').update({ [` favorites.${key}.color `]: true })

Sachin Rathod Over a year ago

This solution is correct. Also alternate solution : db.collection('users').doc('frank').update({ [`favorites.${key}.color `]: true }) and also be careful enough to avoid blank spaces inside [``] section i.e you would end up doing wrong if you include blank space db.collection('users').doc('frank').update({ [` favorites.${key}.color `]: true }

Zack Heisenberg Over a year ago

doesn't make any nested stuff though :/ just update

Sebastijan Dumančić Over a year ago

Note for lurkers: This works for update, but for set it saves as a single prop with dot in it's name, not as a nested property.

|

undefined · Accepted Answer · 2020-03-27 02:36:10Z

35

Just a note about a potential pitfall: After discovering that you can update nested fields using a dot syntax, I tried using set() the same way, since I needed it to work whether the object already exists or not:

var updateObj = {['some.nested.property']: 9000};
docRef.set(updateOb, {merge: true});

Unfortunately, this doesn't work – it sets a property whose key is some.nested.property instead. Inconsistent, but okay.

Fortunately, it appears that set(updateObj, {merge: true}) does a deep merge, so if you construct your update object as a fully nested object, your nested objects will also be properly merged:

// create the object
db.doc('testCollection/doc').set({p1: {['p2']: {p3: true}}}, {merge: true})
// update the existing object
db.doc('testCollection/doc').set({p1: {['p2']: {p4: true}}}, {merge: true})

// result is now this:
{ p1: { p2: { p4: true, p3: true } } }

answered Mar 27, 2020 at 2:36

undefined

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4 Comments

DarkNeuron Over a year ago

Wat. When did they ninja in that? I'm sure it wasn't always like that. It used to do a shallow merge IIRC. But hey, it extremely useful, so thanks for writing about it! 👍🏻

tinyCoder Over a year ago

You made my day man, I was having the same issue for a long time 🥰

Allen Over a year ago

Wow. I had no clue this worked. Very nice. Wish it was documented somewhere.

yet.another.coder Over a year ago

Thanks undefined, you defined everything needed for this

Ronnie Smith · Accepted Answer · 2018-09-10 00:57:06Z

3

You can update specific fields of variable(ly) named nested objects like below.

ref.set({
    name: "Frank",
    favorites: { food: "Pizza", quantity: 2 }
});

//now the relevant update code
var name = "favorites";
var qty = 111;
var update = {};
update[name+".quantity"] = qty;
ref.update(update);

https://jsbin.com/hihifedizu/edit?js,console

answered Sep 10, 2018 at 0:57

Ronnie Smith

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1 Comment

khalidsafir Over a year ago

This is the most useful answer for general use. Thanks for helping me out.

Stefan · Accepted Answer · 2022-08-28 14:50:47Z

2

2022 Update with Webversion 9 (modular):

const docRef = doc(db, 'users', frank); 

var usersUpdate = {};
usersUpdate[`favorites.${key}.color`] = true;

updateDoc(docRef, userUpdate);

answered Aug 28, 2022 at 14:50

Stefan

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1 Comment

David 天宇 Wong Over a year ago

this is the modern answer guys

Fenkan · Accepted Answer · 2022-03-22 03:19:36Z

0

you can use

var auxKey = "history." + someVar;
var dataToUpdate = {
   [auxKey]: "new data generated"
};
db.collection("users").doc("frank").update(dataToUpdate);

answered Mar 22, 2022 at 3:19

Fenkan

11 bronze badge

1 Comment

Fenkan Over a year ago

result: {"history": {"valueOfSomeVar": "new data generated"}}

bad_coder · Accepted Answer · 2021-09-17 05:48:46Z

-1

I felt this is the simplest solutions of all the above :)

db.collection("users").doc("frank").update({
    [`favorites.${KEY}.color`]: true
});

edited Sep 17, 2021 at 5:48

bad_coder

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answered Sep 17, 2021 at 3:47

deepak n

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