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GoJS® Diagramming Components
version 1.8.23 for JavaScript/HTML
by Northwoods Software®

## Class Transaction

A Transaction holds a list of ChangedEvents collected during a transaction, as the value of the read-only changes property.

Start a transaction by calling UndoManager.startTransaction (or Model.startTransaction or Diagram.startTransaction, which call that method). Be sure to finish a transaction with a matching call to UndoManager.commitTransaction (or Model.commitTransaction or Diagram.commitTransaction), or a call to UndoManager.rollbackTransaction (or the same named methods on Model or Diagram).

If you are performing multiple or repeated changes to a model or diagram, surround all of the code with calls to start and commit the transaction -- do not perform repeated calls to start-commit-start-commit. Typically each change caused by the user, such as a button click or a change of focus or a mouse drag, should perform one transaction in which all changes are made. All of the predefined commands and tools perform transactions.

Undoing or redoing a transaction is done by calling UndoManager.undo or UndoManager.redo. Those methods call the undo or redo methods here.

The UndoManager holds a list of Transactions in its UndoManager.history.

## Constructor Summary Details

Name | Description
--- | ---
Transaction() | Construct an object holding an empty list of ChangedEvents and no name.

## Properties Summary Details

Name, Value Type | Description
--- | ---
changes {List.} | This read-only property returns the list of ChangedEvents.More... The changes are stored in order of occurrence. You should not modify this list.
isComplete {boolean} | Gets or sets whether we can add more ChangedEvents to this list of changes.More... This is initially false. It is set to true by UndoManager.commitTransaction and UndoManager.rollbackTransaction.
name {string} | Gets or sets the transaction name for this collection of changes.More... This is set by a top-level call to UndoManager.commitTransaction.

## Method Summary Details

Name, Return Type | Description
--- | ---
canRedo() {boolean} | This predicate returns true if you can call redo, namely when isComplete is true. Returns: {boolean} true if ready for redo to be called.
canUndo() {boolean} | This predicate returns true if you can call undo, namely when isComplete is true. Returns: {boolean} true if ready for undo to be called.
clear() | Clear all of the saved changes.
redo() | Re-perform these changes after an undo.More... This is normally called only by the UndoManager. canRedo must be true for this method to have any effect.
undo() | Undo all of the changes, in reverse order.More... This is normally called only by the UndoManager. canUndo must be true for this method to have any effect.