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The only constant is change: Browsers constantly change. Frameworks constantly change. Tools constantly change. And UI5 consistently evolves. We are working in a rapidly moving target environment and ideally want to benefit from all the innovations happening in every place of the JavaScript ecosystem while on the other side we from UI5 also need to safeguard your investments so that applications which have been built years back continue to work with all the new features and this evolving ecosystem. In my opinion, this is one essential key differentiator to other JavaScript frameworks which is a must for enterprise application development. But although we guarantee to continuously support older applications, we also want to enable the latest APIs, web standards and tools for newly developed applications. Using those features and tools significantly improves the overall development experience and especially the happiness while working with UI5.

Internet Explorer 11 – hmm, what?

Recently, we achieved another big milestone with UI5: we de-support Internet Explorer 11 – finally! Starting with UI5 1.88, the UI5 team removes all IE11 specific polyfills, CSS rules and JavaScript code. A first immediate improvement of the IE11 de-support is that the bootstrap size of UI5 has been reduced by ~50kB (~20kB gzip). This is around 10% of the size of the bootstrap file. And this is just the start. As mentioned above, we will continue to identify and remove more and more places in the UI5 codebase which are related to IE11 and also other legacy browsers to finally clean them up so that the overall code size will be reduced step by step in future versions. Additionally, moving to CSS Variables which are now fully supported by the browser PAM of UI5 1.88 onwards, we can even get rid of our proprietary theme parameters which are inlined in our CSS and migrate them to CSS Variables. This will finally reduce the size of the CSS. And there is much more we can do.

UI5 Evolution

Evolution is a continuous and complicated process. Finally, it never ends. Browsers, frameworks, tools – all of them somehow influence the evolution of the UI5 framework. New features of the browsers or innovations of the tools open up new opportunities. The topology of UI5 is clustered in four different layers: the Modular Core, the Rendering & Controls, the Programming Model and the Tooling. All these layers need to be part of the evolution to stay competitive with other frameworks. UI5 shoulders a heavy burden. On the one hand side, developers expect compatibility over years/decades, on the other hand side they always expect new features and innovations. But this comes with a lot more effort to finally meet all these expectations and implement them with the known qualities. But we wouldn’t be UI5 if we couldn't live up to those expectations. For 2021, more accurately for UI5con 2021 in June, we aim high. Last year, we promised the availability of UI5 Web Components in OpenUI5/SAPUI5 and TypeScript support for UI5 application development. Both topics are being worked on with full speed and I would like to share the current state with you now.

UI5 Web Components in OpenUI5/SAPUI5

The evolution of the Rendering & Controls Framework started in 2018 as part of the UI5 Evolution project. The goal of this project was to decouple the controls and the framework. In addition, we wanted to renovate the rendering engine to get rid of string-based rendering and move to DOM-based rendering. With the evolution of the browser stack and the need to also provide the UI5 controls for other programming models, this finally led us to investigate the latest web standards around Web Components. A long awaited dream come true: a native, browser built-in Control Framework without additional footprint just extending the standard HTML tags of the browser with custom ones, providing fully functional controls! And finally, on top of this we built UI5 Web Components to simplify and structure the development of enterprise-grade Web Components. UI5 Web Components are completely independent from OpenUI5/SAPUI5. With the UI5 Web Components we are able to provide the UI5 Controls as framework-agnostic UI elements. Therefore, the UI5 Controls have been rewritten as Web Components. The UI5 Web Components can now be easily used with any web framework like Svelte, Vue, React or Angular except OpenUI5/SAPUI5.

Finally, with the de-support of Internet Explorer 11, the rendering engine evolution to DOM-based rendering, the usage of CSS Variables and UI5 Tooling, we are now able to put the UI5 Web Components back into OpenUI5/SAPUI5. We will introduce new UI5 libraries which include the so-called wrapper controls for the corresponding UI5 Web Components. The wrapper controls are the connector between the Control Framework and the Web Components. A wrapper control ensures to forward the properties to the Web Component, to put the aggregated controls into slots and to delegate the events. The wrapper control also ensures a well-known paradigm to use the UI5 Web Components in the OpenUI5/SAPUI5 programming model. It allows to use databinding and enables the seamless usage in e.g. XML views.

As of today, the wrapper controls are tightly coupled to UI5 Web Components. The next stage will be to open the wrapper controls to support Web Components in general and to simplify the usage of other Web Components in OpenUI5/SAPUI5.

TypeScript support for UI5 application development

A long-awaited feature is the TypeScript support for UI5 application development. It was first announced at UI5con 2019 with the availability of the UI5 TypeScript project on GitHub. This project has been started to add code-completion support for UI5 for the SAP Web IDE. As this looked really promising, we committed to invest into the TypeScript support.

Supporting TypeScript for UI5 application development turned out to be more complicated than expected. The biggest effort is the clean-up of the JSDoc of the UI5 codebase. As the generation of the TypeScript definition is based on the JSDoc, it needs to contain all relevant information. This task is still in progress and we are pushing for a clean JSDoc for all UI5 libraries of OpenUI5 and the SAPUI5 distribution.

Another important aspect is to define the way UI5 applications should be written in TypeScript. While we have to use the AMD-like syntax (sap.ui.define) and the UI5 classes without TypeScript, we wanted to enable a really modern syntax to develop UI5 applications with TypeScript by using ES modules (import) and ES classes. Finally, we want to use TypeScript as a kind of segue which allows UI5 developers to use a really modern syntax for application development which also benefits from a better IDE support. That allows us to get rid of unwanted Globals and deprecated synchronous APIs. By moving to TypeScript we have somehow a win-win situation by getting rid of the legacy APIs and you can experience a modern development experience.

To achieve all this, we are reworking the tooling to enable TypeScript support for UI5 projects, or more concretely the generator of the TypeScript definitions. Right now, the generator creates TypeScript definitions for the classic syntax (Globals, AMD-like modules and UI5 classes) used in the SAP Web IDE / Business Application Studio development. As our goal is to enable application development with a modern syntax (no Globals, ES modules and ES classes), the generator needs to create those TypeScript defintions in addition to that. Finally, this will allow us to support both scenarios, the recommended scenario is the modern one for sure.

And the last piece is to define the toolchain to transpile the UI5 applications written in TypeScript to JavaScript. The toolchain is based on Babel. It uses the TypeScript plugin to convert the TypeScript code into JavaScript code. When ES modules and ES classes are used the transform-ui5 plugin helps to convert this into the classic UI5 runtime code using AMD-like module syntax and UI5 classes.

All these pieces together will allow UI5 developers to build their UI5 applications with TypeScript using modern JavaScript language features and APIs. The Babel toolchain will ensure proper transpilation of the code into classic UI5 code along with source maps to allow debugging on the TypeScript sources.

Hint: Be careful with using modern language features for UI5 development which require additional polyfills after transpiling. For standalone scenarios, you can easily embed the polyfills whereas for reuse components this is not possible. For UI5 1.88 (no IE11 support) onwards there should only be rare cases for which additional polyfills are needed.

UI5 Community – a joint GitHub organization

The UI5 Tooling laid the foundation of creating an Ecosystem for task and middleware extensions. With the inspiration of the UI5 Ecosystem, many developers in the UI5 community started to develop and share their own custom tasks and middlewares either as part of the UI5 Ecosystem Showcase project or in their own GitHub repositories.

Recently, as a side effect of a discussion about the location of the Ecosystem project, the repository was moved to into an independent UI5 Community GitHub organization to develop, maintain and host UI5 Community projects in a kind of shared responsibility of volunteer full-time UI5 developers and UI5 community developers.

This GitHub organization should become a place in which the generators/templates for creating all different kind of UI5 projects are hosted, like applications, libraries, controls, tasks, middlewares, … and the promise to keep them up-to-date. As we do this jointly, you will learn from the latest best practices from the UI5 development teams and we can also benefit from feedback and ideas of you.

This is just the start of a joint journey and there are some more ideas around the UI5 Community GitHub organization. If you also have ideas, feel free to reach out to us and discuss them in the UI5 Community Home GitHub project by filing an issue.

"We're UI5, folks!" We can define the future together!


Yes, UI5 evolves consistently. The latest developments will take the UI5 development to the next level. Internet Explorer 11 is beyond the horizon. Web Components and CSS Variables will become part of your feature set. The UI5 Tooling is the foundation to benefit from a modern, open and extensible tool chain. TypeScript will power up the development of UI5 application. And the UI5 Community will be a place in which all kind of UI5 developers can work together to define an ecosystem around the UI5 Framework and the UI5 Tooling to get the most out of it. Next stop, UI5con 2021, the event to prove how well all those pieces finally fit together…