collection.update

This method can be used to update a document in a collection. It accepts a json object which specifies the match condition and returns the count of total updated documents. It accepts following arguments

Name	Type	Description
filter	object	a json object which specifies the match condition of documents
update	object	a json object which specifies new values of attributes

It is important to note here that running this function without specifying the match condition will update all the documents of a collection. This method don't overwrites the matched documents entirely but instead only replaces the matched attributes in a document with new values or adds new attributes (if none matched). In other words, if a matched document got structure similar to

{
  voltage: 20,
  current: 2
}

and you run this method with update

{
  voltage: 30,
  power: 60
}

then the document will be updated to

{
  voltage: 30,
  current: 2,
  power: 60
}

This method returns following codes

DATA-INVALID

collection name wasn't specified while getting the reference

DATASTORE-DOCUMENTS-NOT-FOUND

not even a single document qualified the match condition

DATASTORE-DOCUMENTS-UPDATED

updated the matched documents

DATASTORE-DOCUMENTS-UPDATE-FAILED

failed to update the documents

The usage of this method is illustrated in the example below

// Define an update
var update = {
  voltage: 30,
  power: 60
}
 
 
// This method can be used in many ways
 
// Case: update a specific document by providing
// the document id, you can use this on other 
// attributes as well
collection.update({documentID: "id"}, update).then((res) => {
  // Got response from server
  switch(res.code) {
    case "DATASTORE-DOCUMENTS-UPDATED": 
      // Method returns the count
      // should be exactly 1 here
      console.log(res.modifiedCount);
  }
});
 
// Case: update multiple but specific documents
// Define an array of ids of documents required to
// be updated, you can use this on other 
// attributes as well
var documentIDs = ["1", "2", "3"];
 
// Run operation with $in operator
collection.update({documentID: {$in: documentIDs}}, update).then((res) => {
  // Got response from server
  switch(res.code) {
    case "DATASTORE-DOCUMENTS-UPDATED": : 
      // Method returns the count
      // should match the length of the array
      console.log(res.modifiedCount);
  }
});
 
// Case: update in range
// Run operation with $lt and $gt operator on attributes
collection.update({voltage: {$lt: 25, $gt: 30}}, update).then((res) => {
  // Got response from server
  switch(res.code) {
    case "DATASTORE-DOCUMENTS-UPDATED": 
      // Method returns the count
      console.log(res.modifiedCount);
  }
});

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