Angular Basics: DevTools

The Angular DevTools browser extension enhances debugging and profiling specifically in Angular applications. See what features to get started with.

Angular, a framework developed and maintained by Google, is one of today’s most popular tools for building web applications. Its powerful features, such as two-way data binding, dependency injection and modular architecture, make it an excellent choice for crafting dynamic web applications.

In this article, we’ll explore Angular DevTools, a dedicated browser extension designed to enhance debugging and profiling capabilities for Angular applications.

DevTools

In modern web development, DevTools (short for Developer Tools) are essential utilities that allow developers to inspect, debug and optimize their web applications directly from the browser. Most modern browsers, including Chrome and Firefox, have built-in developer tools for debugging JavaScript, analyzing network activity, inspecting the DOM and monitoring performance metrics. These tools help with the understanding of how applications behave under the hood.

Specialized DevTools extensions, such as React DevTools or Vue DevTools, take this further by offering framework-specific insights. They allow developers to navigate the structure of their applications, analyze state changes and identify performance bottlenecks.

Angular DevTools is a framework-specific extension that provides an Angular-centric debugging and profiling experience tailored to the unique architecture of Angular applications.

Angular DevTools

Angular DevTools is a browser extension providing an Angular-specific debugging and profiling interface within our developer tools. It integrates seamlessly with Chrome and Firefox, offering a tailored experience for inspecting and optimizing Angular applications. With Angular DevTools, developers can dive deep into the component structure, debug change detection mechanisms and analyze application performance to identify bottlenecks.

To get started with Angular DevTools, install it from the Chrome Web Store or Firefox Add-ons. Once installed, we can open the browser’s developer tools by pressing F12 (Windows/Linux) or Cmd+Option+I (Mac). If the application we’re inspecting is built with Angular, we’ll find an Angular-specific tab in the developer tools interface.

Let’s take a deeper look into some key functionalities of Angular DevTools.

Components

The Components tab is one of the more powerful features of Angular DevTools. When we open an Angular application in the browser, this tab provides a detailed view of the app’s structure. It displays a tree of components and directives that represent the hierarchy of the application.

We can click on any component in this tree to inspect its properties and metadata on the right-hand side. For instance, we can examine @Input and @Output properties, making it easy to understand the data flow in our application. Angular DevTools also allows us to search for specific components by their names using the search box above the component tree.

If we need to dive deeper into the implementation, we can navigate to the host DOM node of a selected component or directive by double-clicking it. This will redirect us to the Elements tab of our browser’s developer tools. Similarly, we can view the source code of a component by clicking the icon in the top-right corner of the properties panel.

Debugging Properties and Interactions

Angular DevTools doesn’t just let us observe our application; it lets us interact with it as well. In the Components tab, we can edit property values directly. For example, if a component has an input property controlling its behavior, we can update this value in real time to see how it affects the application.

Additionally, Angular DevTools integrates with the browser’s console for direct interaction with selected components or directives. By typing $ng0, we can access the most recently selected component instance. Previous instances can be accessed using $ng1, $ng2 and so on. This feature is especially useful for testing methods and properties during runtime.

Profiler

The Profiler tab is essential for understanding how our Angular application performs during change detection cycles. This tab allows us to record and visualize our app’s performance, identifying areas where improvements can be made.

When we start recording, the Profiler tracks change detection events and displays them as a bar chart. Each bar represents a single change detection cycle, with its height indicating the time spent. Clicking on a bar provides further insights, including which components or directives took the most time to render.

For a more detailed view, Angular DevTools offers a flame graph representation. The flame graph shows the hierarchy of components and how much time each consumed during a change detection cycle. Components that took longer to render appear with more intense colors, helping us quickly identify potential bottlenecks.

Injector Tree

The Injector Tree feature visualizes our dependency injection hierarchy for Angular applications built with version 17 or higher. This feature is invaluable when debugging services, providers or dependency resolution paths.

The Injector Tree displays two views: the environment hierarchy and the element hierarchy, each representing how dependencies are resolved in an application. By selecting an injector, we can see all the providers it contains and the resolution path Angular follows to fulfill dependencies. This makes identifying and fixing misconfigurations in our dependency injection setup easier.

Wrap-up

Angular DevTools is a practical extension for developers working with Angular applications. Its features, such as the Components tab, Profiler tab and Injector Tree, provide valuable insights into application structure, performance and dependency resolution. These tools make it easier to debug, optimize and better understand the behavior of Angular applications, enabling developers to address issues efficiently and refine their codebase effectively.

In this article, we’ve highlighted some of the core functionalities of Angular DevTools, but there’s more to explore. For additional details and a complete overview of what Angular DevTools offers, visit the official Angular DevTools documentation, which also served as the reference for the images used in this article.