class

DocumentChange

Source: document-change.js:35

A DocumentChange represents a change to the documents matching a query. It contains the document affected and the type of change that occurred.

Properties

doc
newIndex
oldIndex
type

Method

isEqual(other)

Properties

read-only

doc  QueryDocumentSnapshot

The document affected by this change.

Example 

let query = firestore.collection('col').where('foo', '==', 'bar');

let unsubscribe = query.onSnapshot(querySnapshot => {
  for (let change of querySnapshot.docChanges) {
    console.log(change.doc.data());
  }
});

// Remove this listener.
unsubscribe();
read-only

newIndex  number

The index of the changed document in the result set immediately after this DocumentChange (i.e. supposing that all prior DocumentChange objects and the current DocumentChange object have been applied). Is -1 for 'removed' events.

Example 

let query = firestore.collection('col').where('foo', '==', 'bar');
let docsArray = [];

let unsubscribe = query.onSnapshot(querySnapshot => {
  for (let change of querySnapshot.docChanges) {
    if (change.oldIndex !== -1) {
      docsArray.splice(change.oldIndex, 1);
    }
    if (change.newIndex !== -1) {
      docsArray.splice(change.newIndex, 0, change.doc);
    }
  }
});

// Remove this listener.
unsubscribe();
read-only

oldIndex  number

The index of the changed document in the result set immediately prior to this DocumentChange (i.e. supposing that all prior DocumentChange objects have been applied). Is -1 for 'added' events.

Example 

let query = firestore.collection('col').where('foo', '==', 'bar');
let docsArray = [];

let unsubscribe = query.onSnapshot(querySnapshot => {
  for (let change of querySnapshot.docChanges) {
    if (change.oldIndex !== -1) {
      docsArray.splice(change.oldIndex, 1);
    }
    if (change.newIndex !== -1) {
      docsArray.splice(change.newIndex, 0, change.doc);
    }
  }
});

// Remove this listener.
unsubscribe();
read-only

type  string

The type of change ('added', 'modified', or 'removed').

Example 

let query = firestore.collection('col').where('foo', '==', 'bar');
let docsArray = [];

let unsubscribe = query.onSnapshot(querySnapshot => {
  for (let change of querySnapshot.docChanges) {
    console.log(`Type of change is ${change.type}`);
  }
});

// Remove this listener.
unsubscribe();

Method

isEqual(other)

Returns true if the data in this DocumentChange is equal to the provided value.

Parameter

Name Type Optional Description

other

any type

 

The value to compare against.
Returns

true if this DocumentChange is equal to the provided value.