0We use $[] to update all items inside an array in a document at once. It helps change many values without writing separate commands for each.
db.collection.updateMany(
{ <filter> },
{ $set: { "arrayField.$[]": <newValue> } }
)The $[] is called the 'all positional operator'. It targets every element in the array.
You must specify the array field name before $[], like arrayField.$[].
tasks array to the string "done" for all users.db.users.updateMany(
{},
{ $set: { "tasks.$[]": "done" } }
)shipped field as true for every item in the items array, but only for orders with status "pending".db.orders.updateMany(
{ status: "pending" },
{ $set: { "items.$[].shipped": true } }
)prices array by 5 for all products.db.products.updateMany(
{},
{ $inc: { "prices.$[]": 5 } }
)This example creates a students collection with two documents. Each has a grades array. We add 5 points to every grade using $inc with the $[] operator.
db.students.insertMany([
{ _id: 1, name: "Alice", grades: [70, 80, 90] },
{ _id: 2, name: "Bob", grades: [60, 75, 85] }
])
// Show before update
print("Before update:")
db.students.find({}, { _id: 0, name: 1, grades: 1 }).forEach(doc => printjson(doc))
// Update: add 5 points to every grade for all students
// Using $inc with $[] to update all elements in grades array
db.students.updateMany(
{},
{ $inc: { "grades.$[]": 5 } }
)
// Show after update
print("After update:")
db.students.find({}, { _id: 0, name: 1, grades: 1 }).forEach(doc => printjson(doc))The $[] operator updates all elements in an array, unlike $ which updates only the first matching element.
Operators like $set and $inc are supported with $[] for arrays of primitives and subfields in objects.
Remember to test updates on a small dataset first to avoid unwanted changes.
$[] updates every element in an array inside documents.
It is useful when you want to change all items without looping manually.
For complex transformations, use aggregation pipeline with $map.
$[] operator do in a MongoDB update query?$[]$[] operator is called the all positional operator and targets all elements in an array during an update.$ which updates the first matched element, $[] updates every element in the array.$[] updates all array elements [OK]scores array by 1 using $[] in MongoDB?$inc operator increments numeric values. Using 'scores.$[]' targets all elements in the array.$inc with $[] to increment each element by 1. Other options either use wrong operators or wrong field paths.{ _id: 1, scores: [10, 20, 30] }, what will be the scores array after running this update?db.collection.updateOne({_id:1}, { $inc: { 'scores.$[]': 5 } })$inc with 'scores.$[]', which increments every element in the scores array by 5.ratings array by multiplying each by 2. Which update query will cause an error?$mul, $inc, and $set can work with $[] to update array elements. $push is for adding elements, not updating existing ones.$push with $[] is invalid and causes an error because $push expects a field name without positional operators.items as an array of objects like { _id: 1, items: [{qty: 2}, {qty: 5}] }. You want to add 3 to the qty of every item. Which update query correctly does this?items with objects containing qty. We want to add 3 to each qty.$inc with items.$[].qty, which correctly increments the qty field of every object in the array. db.collection.updateMany({}, { $set: { items: { $map: { input: "$items", as: "item", in: { qty: { $add: ["$$item.qty", 3] } } } } } }) attempts to use aggregation operators like $map in a simple update, which requires pipeline syntax (array of stages) and is invalid. db.collection.updateMany({}, { $set: { 'items.$[].qty': { $add: ['items.$[].qty', 3] } } }) is invalid syntax. db.collection.updateMany({}, { $push: { 'items.$[].qty': 3 } }) misuses $push.Pass the test and this pattern moves unknown strong while earning +1 Grip toward your certificate.