10 Tips to Fix Runtime Error Due to Production Builds Angular Application

Runtime errors during production builds in Angular applications can be frustrating, especially when the development environment works seamlessly. These errors often stem from misconfigurations, code inconsistencies, or unoptimized settings specific to the production environment. This article will delve into common causes of runtime errors in production builds, practical solutions, and best practices to ensure smooth deployment.

Understanding Runtime Errors in Angular Production Builds

Runtime errors occur when code that runs perfectly in development encounters problems in production. Angular’s production build (ng build --prod) optimizes and minifies code to improve performance, which may expose underlying issues. Common symptoms include broken functionality, missing assets, or crashes upon application load.

Common Causes of Runtime Errors in Production

• Missing Production-Specific Configuration
  Development configurations often differ from production. If production-specific configurations are incomplete or incorrect, errors can occur.
• Unoptimized Lazy Loading
  Incorrect route configurations for lazy-loaded modules may cause navigation issues or module failures.
• Improper Usage of Third-Party Libraries
  Some libraries may behave differently in production due to code minification or tree-shaking.
• Missing or Misconfigured Polyfills
  Older browsers may fail to run modern JavaScript features if polyfills are not included.
• Uncaught Errors During Optimization
  Angular’s optimization process can expose coding issues like missing types, unused imports, or bad logic.
• Environment Variable Mismanagement
  Failing to properly configure environment-specific settings may cause mismatches between development and production.
• Uncaught Errors in Templates
  Errors in Angular templates, such as null references or bindings, might only surface in production.

Step-by-Step Guide to Fix Runtime Errors

Step 1: Verify Build Command

Always use the correct command for production builds:

ng build --prod

Step 2: Enable Debugging for Production Builds

To better understand runtime errors, include source maps in your production build:

ng build --prod --source-map

Step 3: Check Environment Files

Ensure your environment files (environment.ts, environment.prod.ts) are configured correctly. For instance, verify API endpoints or feature toggles:

export const environment = {
  production: true,
  apiEndpoint: 'https://api.example.com'
};

Step 4: Optimize Lazy Loading

Incorrect lazy loading can lead to runtime errors. Verify module paths in AppRoutingModule:

const routes: Routes = [
  { path: 'feature', loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule) }
];

Step 5: Update Third-Party Libraries

Outdated libraries can cause compatibility issues. Update dependencies in package.json:

npm outdated
npm install <package-name>@latest

Step 6: Include Necessary Polyfills

Ensure the polyfills.ts file includes compatibility for older browsers:

import 'zone.js/dist/zone'; // Required for Angular
import 'core-js/features/array/includes'; // Example polyfill

Step 7: Handle Null References

Errors like Cannot read property of null often arise in templates. Use safe navigation operators (?.) to prevent such errors:

<p>{{ user?.name }}</p>

Step 8: Check for Global Variables

Avoid relying on global variables or browser-specific behaviors. Use Angular’s dependency injection system to manage shared resources.

Step 9: Run a Pre-Deployment Test

Run the production build locally to catch errors before deployment:

ng serve --prod

Ensure all templates, decorators, and Angular modules adhere to AOT requirements:

• Avoid dynamic templates.
• Declare all components and modules explicitly.
• Ensure all types are correctly defined.

Best Practices for Avoiding Runtime Errors

1. Use TypeScript Strict Mode

Enable strict mode in tsconfig.json to catch potential errors during development:

"strict": true,
"noImplicitAny": true

2. Conduct Code Audits

Regularly review your codebase for unused imports, undefined variables, or potential pitfalls.

3. Monitor Browser Compatibility

Use tools like Can I Use to ensure your application supports target browsers.

4. Implement Comprehensive Testing

Use unit tests and end-to-end tests to validate functionality. Tools like Jasmine and Protractor can help automate testing.

5. Leverage Linting Tools

Linting tools like ESLint can identify code issues early. Configure Angular’s linting rules in angular.json.

6. Use CI/CD Pipelines

Integrate a CI/CD pipeline to automate builds, tests, and deployments. This reduces the chance of human error.

Examples of Fixes

Fixing a Null Reference Error

Before:

<p>{{ user.name }}</p>

After:

<p>{{ user?.name }}</p>

Fixing Lazy Loading Issue

Before:

const routes: Routes = [
  { path: 'feature', loadChildren: './feature/feature.module#FeatureModule' }
];

After:

const routes: Routes = [
  { path: 'feature', loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule) }
];

Conclusion

Yury Sobolev

Yury Sobolev is Full Stack Software Developer by passion and profession working on Microsoft ASP.NET Core. Also he has hands-on experience on working with Angular, Backbone, React, ASP.NET Core Web API, Restful Web Services, WCF, SQL Server.