Debugging Angular Apps: How to Use Chrome DevTools

Debugging is an essential aspect of web development that enables developers to detect and fix problems effectively. In the case of Angular apps, Chrome DevTools provides an effective collection of tools for inspecting elements, observing network requests, and debugging code. In this blog, we discuss useful tips on using Chrome DevTools to debug Angular apps effectively.

Chrome DevTools is a collection of web development tools integrated directly into the Google Chrome browser. It offers functionality like:

Element Inspection: Inspect and edit the DOM and CSS in real-time.

• Console: Run JavaScript and examine application states.
• Sources: Place breakpoints and step through code.
• Network: Observe API requests and responses.
• Performance: Examine load times and performance bottlenecks.

Angular's dynamic rendering sometimes makes it hard to debug UI problems. DevTools Elements tab enables you to:

View and edit HTML and CSS live.

• Detect style overrides and specificity problems.
• Debug responsive designs through the device toolbar.

Example: Editing Styles on the Fly

1. Right-click the element and choose Inspect.
2. Go to the Styles pane and edit CSS.
3. Changes are executed directly in the browser, and you can rapidly prototype.

The Console tab is not only for displaying errors. It can be employed to communicate directly with your Angular application.

Tip: Access Angular Components in Console

You can access Angular components through ng debugging tools:

ng.probe($0).componentInstance

$0 is a reference to the element selected in the Elements tab.

Inspect component properties and invoke component methods directly.

Useful Console Commands

• console.log(): Print variable values or debug information.
• console.table(): Print arrays or objects in table format.
• console.error(): Print error messages prominently.

Breakpoints enable you to stop code execution and examine variable values and the call stack.

How to Set Breakpoints

• Navigate to the Sources tab.
• Open your TypeScript file under File System or Page.
• Click on the line number to set a breakpoint.
• Reload the page or cause the particular code execution.
• Advanced Breakpoint Techniques

Conditional Breakpoints: Right-click on the line number, and create conditions to break only when conditions are fulfilled.

XHR Breakpoints: Break apart specific API calls by breaking on XMLHttpRequest or fetch events.

When your Angular application communicates with APIs, it is important to monitor network requests.

Employing the Network Tab

1. Filter Requests: By type (e.g., XHR for API calls).
2. View Request/Response Details: Observe headers, payloads, and status codes.
3. Simulate Network Conditions: Evaluate performance during slow network conditions through Throttling.
4. Debugging API Calls
5. Monitor request payloads and parameters.
6. Verify errors in responses or HTTP status codes.
7. Replay failing requests by right-clicking and selecting Replay XHR.

The Performance tab gives rendering and scripting performance insights.

Steps for Performance Profiling

1. Open the Performance tab and click on Record.
2. Toggle your Angular application (e.g., load a page or tap a button).
3. Stop recording to analyze the performance timeline.
4. Identifying Performance Bottlenecks
5. Look for long tasks or red warnings in the timeline.
6. Identify which scripts or resources are causing delays.

Bonus Tip: Using Augury for Angular

In addition to Chrome DevTools, consider using Augury, a Chrome extension specifically for debugging Angular applications.

1. Component Tree: Visualize Angular components and their hierarchies.
2. Router Tree: Inspect the Angular router state.
3. State Inspection: View component properties and services.

Debugging Angular apps with Chrome DevTools can really optimize your development process. From viewing elements and tracing network requests to setting breakpoints and profiling performance, these tools have got you covered. With DevTools and Angular-specific tools like Augury, you can optimize your productivity and develop more stable applications.

Happy Debugging!

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