How to Check for Session Changes

• The session's advanced property hasChanges indicates whether any entities were added, modified, or deleted within the session.

• Note: The hasChanges property is cleared after calling saveChanges().

const session = store.openSession();

// No changes made yet - 'hasChanges' will be FALSE
assert.ok(!session.advanced.hasChanges());

// Store a new entity within the session
const employee = new Employee();
employee.firstName = "John";
employee.lastName = "Doe";

await session.store(employee);

// 'hasChanges' will now be TRUE
assert.ok(session.advanced.hasChanges());

// 'hasChanges' will reset to FALSE after saving changes 
await session.saveChanges();
assert.ok(!session.advanced.hasChanges());

• Use the session's advanced method whatChanged() to get all changes made to all the entities tracked by the session.

• For each entity that was modified, the details will include:

  • The name and path of the changed field
  • Its old and new values
  • The type of change

• Note: whatChanged() reports changes made prior to calling saveChanges().
  Calling it immediately after saveChanges will return no results, as the changes are cleared.

Example I

const session = store.openSession();

// Store (add) new entities, they will be tracked by the session
const employee1 = new Employee();
employee1.firstName = "John";
employee1.lastName = "Doe";

const employee2 = new Employee();
employee2.firstName = "Jane";
employee2.lastName = "Doe";

await session.store(employee1, "employees/1-A");
await session.store(employee2, "employees/2-A");

// Call 'WhatChanged' to get all changes in the session
const changes = session.advanced.whatChanged();
assert.equal(Object.keys(changes).length, 2);  // 2 entities were added

// Get the change details for an entity, specify the entity ID
const changesForEmployee = changes["employees/1-A"];
assert.equal(Object.keys(changesForEmployee).length, 1); // a single change for this entity (adding)

// Get the change type
const changeType = changesForEmployee[0].change;
assert.equal(changeType, "DocumentAdded");

await session.saveChanges();

Example II

const session = store.openSession();

// Load the entities, they will be tracked by the session
const employee1 = await session.load("employees/1-A");
const employee2 = await session.load("employees/2-A");

// Modify entities
employee1.firstName = "Jim";
employee1.lastName = "Brown";
employee2.lastName = "Smith";

// Delete an entity
session.delete(employee2);

// Call 'WhatChanged' to get all changes in the session
const changes = session.advanced.whatChanged();

// Get the change details for an entity, specify the entity ID
let changesForEmployee = changes["employees/1-A"];

assert.equal(changesForEmployee[0].fieldName, "firstName");  // Field name
assert.equal(changesForEmployee[0].fieldNewValue, "Jim");    // New value
assert.equal(changesForEmployee[0].change, "FieldChanged");  // Change type

assert.equal(changesForEmployee[1].fieldName, "lastName");
assert.equal(changesForEmployee[1].fieldNewValue, "Brown");
assert.equal(changesForEmployee[1].change, "FieldChanged");

// Note: for employee2 - even though the LastName was changed to 'Smith',
// the only reported change is the latest modification, which is the delete action. 
changesForEmployee = changes["employees/2-A"];
assert.equal(changesForEmployee[0].change, "DocumentDeleted");

await session.saveChanges();

// HasChanges
session.advanced.hasChanges();

// WhatChanged
session.advanced.whatChanged();