A set of Angular components to manage GoJS Diagrams, Palettes, and Overviews

pushedAt 1 month ago



Version 2.0

By Northwoods Software for GoJS 2.1

This project provides Angular components for GoJS Diagrams, Palettes, and Overviews to simplify usage of GoJS within an Angular application. The implementation for these components is inside the projects/gojs-angular folder. See the gojs-angular-basic project for example usage and the Intro page on using GoJS with Angular for more information.

Version 2.0 expects immutability of all @Input properties to Diagram|Palette|Overview components, and removes skipsPaletteUpdate and modelChange properties from PaletteComponent.


gojs-angular can be installed via NPM. This package has peer dependencies on GoJS and Angular, so make sure those are also installed or included on your page.


npm install --save gojs-angular

Making Changes

If you want to change how the GoJS / Angular components are implemented, you will need to edit the files in projects/gojs-angular, then, from the main directory, run

npm run package

which will create a new package in the folder, dist/angular-gojs, for you to use. Currently, gojs-angular depends on TypeScript and immer.


This package provides three components - DiagramComponent, PaletteComponent, and OverviewComponent - corresponding to the related GoJS classes.

Note: As of version 2.0, gojs-angular assumes immutability of the @Input properties given to Diagram/Palette components. The gojs-angular-basic repository provides example usage of these components, as well as preserving state immutability (that project uses immer to maintain immutability, but you can use whatever you like best).

Below is an example of how you might pass properties to each of the components provided by gojs-angular. Here, for immutable data properties that may change, they are stored in an object called state. This is not required, but helps with organization.




Component Properties


Specifies a function that is reponsible for initializing and returning a GoJS Diagram, Palette, or Overview. In the case of an Overview, this is an optional property and when not provided, an Overview with default properties and centered content will be created.

function initDiagram() {
  const $ = go.GraphObject.make;

  const diagram = $(go.Diagram,
      'undoManager.isEnabled': true,
      model: $(go.GraphLinksModel, {
        linkKeyProperty: 'key'  // this should always be set when using a GraphLinksModel

  diagram.nodeTemplate =
    $(go.Node, 'Auto',  // the Shape will go around the TextBlock
      $(go.Shape, 'RoundedRectangle', { strokeWidth: 0, fill: 'white' },
        // Shape.fill is bound to Node.data.color
        new go.Binding('fill', 'color')),
        { margin: 8 },  // some room around the text
        // TextBlock.text is bound to Node.data.key
        new go.Binding('text', 'key'))

  return diagram;


Specifies the CSS classname to add to the rendered div. This should usually specify a width/height.

.myDiagramDiv {
  width: 400px;
  height: 400px;
  border: 1px solid black;

nodeDataArray (DiagramComponent and PaletteComponent only)

Specifies the array of nodes for the Diagram's model.

nodeDataArray: [
  { key: 'Alpha', color: 'lightblue' },
  { key: 'Beta', color: 'orange' },
  { key: 'Gamma', color: 'lightgreen' },
  { key: 'Delta', color: 'pink' }

Optional - linkDataArray (DiagramComponent and PaletteComponent only)

Specifies the array of links for the Diagram's model, only needed when using a GraphLinksModel, not for Models or TreeModels. If are using this property, make sure to set the GraphLinksModel's linkKeyProperty in its corresponding initDiagram or initPalette function.

linkDataArray: [
  { key: -1, from: 'Alpha', to: 'Beta' },
  { key: -2, from: 'Alpha', to: 'Gamma' },
  { key: -3, from: 'Beta', to: 'Beta' },
  { key: -4, from: 'Gamma', to: 'Delta' },
  { key: -5, from: 'Delta', to: 'Alpha' }

Optional - modelData (DiagramComponent and PaletteComponent only)

Specifies a shared modelData object for the Diagram's model.

skipsDiagramUpdate (DiagramComponent only)

Specifies whether the Diagram component should skip updating, often set to true when updating state from a GoJS model change.

Because GoJS Palettes are read-only by default, this property is not present in PaletteComponent.

modelChange (DiagramComponent)

Specifies a function to be called when a GoJS transaction has completed. This function will typically be responsible for updating app-level state. Remember, these state properties are assumed to be immutable. This example modelChange, is taken from the gojs-angular-basic project, which uses immer's produce function to maintain immutability.

It is important that state updates made in this function include setting skipsDiagramUpdate to true, since the changes are known by GoJS.

Because GoJS Palettes are read-only by default, this property is not present on PaletteComponent. Although there won't be user-driven changes to a Palette's model due to the read-only nature of Palettes, changes to the nodeDataArray, linkDataArray, or shared modelData props described above allow for a Palette's model to be changed, if necessary.

// When the diagram model changes, update app data to reflect those changes. Be sure to preserve immutability
  public diagramModelChange = function(changes: go.IncrementalData) {
    const appComp = this;
    this.state = produce(this.state, draft => {
      // set skipsDiagramUpdate: true since GoJS already has this update
      draft.skipsDiagramUpdate = true;
      draft.diagramNodeData = DataSyncService.syncNodeData(changes, draft.diagramNodeData, appComp.observedDiagram.model);
      draft.diagramLinkData = DataSyncService.syncLinkData(changes, draft.diagramLinkData, appComp.observedDiagram.model);
      draft.diagramModelData = DataSyncService.syncModelData(changes, draft.diagramModelData);

Notice the use of the three static functions of the DataSyncService (syncNodeData, syncLinkData, and syncModelData), which is included with this package to make syncing your app-level data with Diagram / Palette data simple. Be aware: If you have set your Diagram's model.nodeKeyProperty or model.linkKeyProperty to anything other than 'key', you will need to pass your Diagram's model as a third parameter to DataSyncService.syncNodeData and DataSyncService.syncLinkData.

observedDiagram (OverviewComponent only)

Specifies the Diagram which the Overview will observe.

Migrating to Version 2.0

This page assumes use of gojs-angular version 2.0, which requires immutable state, unlike version 1.0. It is recommended to use the 2.0 version. If you have a gojs-angular project using version 1.x and want to upgrade, reference this section for tips on migrating to version 2.

Should I upgrade?

In general, yes.

If you have very simple node and link data, using the latest 1.x version might be okay. But new features and quality of life changes will be published on the 2.x branch moving forward.

Version 2.0 handles complex nested data much better than the previous version, due to its focus on immutable data. Additionally, it is a bit smaller in file size.

One may wish to hold off on upgrading if they have lots of operations mutating their @Input properties, and they do not want to take the time to rewrite those operations immutably. However, the guide below details one way one could do this. Our gojs-angular-basic sample also has demonstrations of immutably updating @Input properties to make such a rewrite easier.

Upgrade gojs-angular Version

Update your package.json to require gojs-angular version 2.0 or greater, then run npm install.

It is also recommended to upgrade to the lastest version of gojs.


The biggest change with 2.0 is you must enforce immutability of @Input properties to your Diagram and Palette components.

So, for instance, whenever an entry of diagramNodeData is updated, removed, or changed, you will need to generate a whole new Array for DiagramComponent.diagramNodeData. This can be done in many different ways with many different packages. A popular choice is immer, which exposes a produce function that allows one to immutability manipulate their data on a draft variable. We will use that function here for demonstration purposes.

The Version 1.0 Way

In gojs-angular version 1, if you wanted to add some node data to your diagramNodeData @Input property, you could do so by simply adding to the diagramNodeData Array, mutating it. Such as:

// When the diagram model changes, update app data to reflect those changes
public addNode = function(nodeData: go.ObjectData) {
  this.skipsDiagramUpdate = false; // sync changes with GoJS model
The Version 2.0 Way

In gojs-angular version 2, that same addNode function must be changed so the diagramNodeData property is updated immutably (that is, replaced with an entirely new Array). Here is an example of doing that with immer's produce function.

// When the diagram model changes, update app data to reflect those changes
public addNode = function(nodeData: go.ObjectData) {
  this.state = produce(this.state, draft => {
    var nodedata = { id: "Zeta", text: "Zorro", color: "red" };
    draft.skipsDiagramUpdate = false;

Notice we are also using a massive state object to hold gojs-angular component properties. This makes these kinds of immutable operations (especially if you are using immer, or a package like it) straightforward (see how we were able to update both skipsDiagramUpdate and diagramNodeData on the same draft variable).

To see more samples of enforcing immutability with gojs-angular, see gojs-angular-basic, particularly the modelChange property of the Diagram Component.

Additional Considerations

Additionally, as of 2.0, PaletteComponent no longer supports skipsPaletteUpdate or modelChange properties. As GoJS Palettes are read-only by default, their models should not be changing based on user input. Instead, if you need to update their node/link/model data, update their @Input properties (immutably, of course).


This project is intended to be used alongside GoJS, and is covered by the GoJS software license.

Copyright 1998-2021 by Northwoods Software Corporation.

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