General guidelines for developing widgets

  • Release version: Xanadu
  • Updated August 1, 2024
  • 4 minutes to read
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    Summary of General guidelines for developing widgets

    These guidelines provide best practices for developing custom widgets in ServiceNow to ensure optimal performance, scalable development, and a positive user experience. They address initial widget configuration, data handling, code reuse, event management, server communication, and user interface considerations.

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    Key Guidelines

    • Create a meaningful default state: Design widgets with a default state or demo data that clearly communicates required configurations to administrators and demonstrates functionality during preview.
    • Embed widgets instead of cloning: Embed existing widgets when possible to leverage existing functionality and reduce code duplication, passing parameters to control behavior.
    • Limit large data sets: Avoid querying or processing large data volumes to improve performance. Use limits, filters, and isolate heavy data widgets on separate pages. Avoid auto-refreshing widgets and unfiltered record watchers, and always apply the setLimit method to GlideRecord queries, optionally tying limits to instance options.
    • Use directives for lightweight reusable components: When only a widget subsection is needed, create Angular directives instead of embedding the entire widget to reduce overhead and facilitate sharing UI features or custom behaviors.
    • Share data and state with services or factories: Use Angular services or factories to maintain state, synchronize widgets, share data across widgets, and reduce server calls.
    • Handle events with publish/subscribe services: Avoid expensive $broadcast calls; use a publish/subscribe pattern for better control and efficiency in event handling between widgets.
    • Fetch data efficiently with REST calls or server.get: Minimize use of server.update() which reloads the entire widget. Use scripted REST APIs and server.get with input.action to separate business logic from UI code and improve maintainability.
    • Design for localization, accessibility, and UI responsiveness: Ensure widgets work well on mobile devices by avoiding mouse-over events, use SCSS variables and color names for styling consistency, and wrap strings for translation using localization APIs.
    • Maintain clean client scripts: Remove unused Angular Providers from client script functions to improve maintainability.
    • Avoid inline <script> tags in templates: Use Angular ng-template records instead to prevent production issues in Service Portal.

    Benefits for ServiceNow Customers

    Following these guidelines helps customers develop performant, maintainable, and user-friendly widgets that integrate seamlessly into the Service Portal. They enable efficient data handling, code reuse, and event management, ultimately delivering a scalable and responsive user experience across devices while simplifying ongoing maintenance and customization.

    When developing custom widgets, keep these general guidelines in mind for optimal performance, scalable development, and a good user experience.

    Create a default state that provides an example to the end user

    A widget does not have instance options defined when initially added to a page. A widget in this empty state can appear blank and cause confusion. In situations where a widget requires some initial configuration, ensure that your widget has a default state that communicates to the admin what configuration is necessary.

    Widgets can also be created with demo data. Demo data can also be used to:

    • Clearly demonstrate the widget functionality to the user.
    • Provide data when previewing the widget in the widget editor. (Demo data is not visible in the designer).

    Learn more: Tutorial: Build a custom widget.

    Embed a widget rather than clone when possible

    Embedding an existing widget into your custom widget takes advantage of pre-existing functionality without cloning or duplicating code. You can still pass parameters into the embedded widget to control its behavior.

    Learn more: Embed an existing widget

    Avoid using large data sets to improve performance

    Querying data, evaluating ACLs, running business rules, and data processing take time and can slow performance. Determine how much data portal users need and then apply the appropriate limits and filters to your scripts and queries. Isolate widgets that require significant data or processing to their own separate pages in the portal. Avoid implementing the following items that use large data sets:

    • Scripted menu items that load large amounts of data, which can cause every page in the portal to load slowly.
    • Large files and attachments, such as high-definition media files or fonts from the Attachments [sys_attachment] table.
    • Auto-refreshing widgets. Every time a widget's client controller calls server.update(), spUtil.update(), server.refresh(), or spUtil.refresh(), the application runs the widget's server script and sends a data object back to the client.
    • Unfiltered record watchers. The recordWatch() function watches for updates to a table or filter and returns the value from the callback function. Adding filters for specific fields to watch reduces the number of calls a widget makes to the server. Specifying when to refresh widgets in response to a record producer notifying the client that there is an update in the callback function can also improve performance.
    • Server-side scripts with GlideRecord queries without the setLimit function. Using the setLimit function can restrict the number of records returned and improve response time on queries. For added flexibility, you can tie this limit to an instance option rather than assigning a hard-coded value (for example: gr.setLimit(options.limit || 100)).
    Learn more:
    Create a directive instead of embedding a complex widget

    When an embedded widget is called from the server, all the scripts associated with that widget are returned. If you only need a subsection of a widget, embedding the entire widget creates unnecessary overhead. Instead, use directives to share lightweight code between widgets. Directives are useful, for example, when building UI components. Complex components with server-side and client-side functionality are best left as widgets. Use a directive instead of an embedded widget to:

    • Share scope or custom scope behavior with multiple widgets.
    • Share a reusable, lightweight subsection of a widget.
    • Share a common UI feature, such as a list or an avatar.
    • Augment widget behavior.

    Learn more: Reuse components with Angular Providers.

    Use a service or factory to share data and persist state

    Data services and factories maintain and persist state in a widget without requiring multiple calls to the server, enabling you to:

    • Keep widgets synchronized when changing records or filters.
    • Share data between widgets.
    • Develop more performant widgets.

    Learn more: Reuse components with Angular Providers.

    Handle events with a publish/subscribe service

    Avoid using $broadcast in the DOM. $broadcast dispatches the event name to all child scopes notifying registered listeners, which can be an expensive call that requires the use of the $rootScope global object.

    Instead, use a publish/subscribe service to handle events. When using a publish/subscribe service, a clear relationship forms between your widgets through callback handlers. In this model, you can better control the state of your events.

    Use REST calls or server.get to fetch data from the server

    When you call server.update(), the entire widget is returned from the server. If your widget includes divergent code paths, multiple calls to update the server can affect performance. As a rule, use your server script to set up the initial state of your widget. For subsequent updates, use scripted REST APIs that call script includes on your instance. This practice:

    • Separates business logic from UI elements.
    • Centralizes your code, allowing changes to be made in one place.
    You can also use server.get to pass information to the server. Use this function along with input.action to execute specific parts of the server script.
    Develop with localization, accessibility, and UI in mind

    To create the best experience for your users, follow these guidelines:

    • Consider the impact of your widget in a mobile environment. For example, avoid using mouse-over and other events that do not translate to a mobile device.
    • Use SCSS variables to reuse items. See SCSS variables.
    • Use variable names when using colors.
    • Wrap strings for translation in localization APIs. See Internationalize a widget.
    Remove unused Angular Providers from client script
    For easier maintenance, remove any unused Angular Providers that were injected into the client script function statement.
    Avoid using <script> tags in HTML templates
    To lessen the likelihood of production issues in Service Portal, avoid using inline templates using <script> tags in a widget's HTML template. Instead, create a related Angular ng-template record for the widget.