nest-feature-flags

Professional feature flag management system for NestJS with A/B testing, gradual rollouts, user targeting, and real-time updates.

🚀 Features

• Feature Toggles - Enable/disable features instantly
• Gradual Rollouts - Percentage-based feature releases
• A/B Testing - Run experiments with user segmentation
• User Targeting - Target specific users or groups
• Real-time Updates - Changes reflect immediately
• Type-Safe - Full TypeScript support
• Production-Ready - Built for enterprise applications

📦 Installation

npm install nest-feature-flags

🔧 Quick Start

1. Import Module

import { Module } from '@nestjs/common';
import { FeatureFlagsModule } from 'nest-feature-flags';

@Module({
  imports: [
    FeatureFlagsModule.forRoot({
      flags: {
        'new-ui': { enabled: true },
        'beta-feature': { enabled: false },
        'gradual-rollout': { enabled: true, percentage: 50 },
      },
    }),
  ],
})
export class AppModule {}

2. Use in Services

import { Injectable } from '@nestjs/common';
import { FeatureFlagService } from 'nest-feature-flags';

@Injectable()
export class MyService {
  constructor(private featureFlags: FeatureFlagService) {}

  async doSomething(userId: string) {
    if (await this.featureFlags.isEnabled('new-ui', { userId })) {
      return 'New UI experience';
    }
    return 'Classic UI';
  }
}

3. Use Guards

import { Controller, Get, UseGuards } from '@nestjs/common';
import { FeatureFlagGuard, RequireFeature } from 'nest-feature-flags';

@Controller('beta')
export class BetaController {
  @Get()
  @UseGuards(FeatureFlagGuard)
  @RequireFeature('beta-feature')
  async betaEndpoint() {
    return { message: 'Beta feature active!' };
  }
}

📖 Documentation

Feature Flag Configuration

{
  'flag-name': {
    enabled: true,              // Master switch
    percentage: 50,             // Gradual rollout (0-100)
    userIds: ['user1', 'user2'], // Specific users
    groups: ['beta-testers'],    // User groups
    startDate: new Date(),       // Schedule activation
    endDate: new Date(),         // Schedule deactivation
  }
}

Advanced Usage

Percentage-based Rollout

FeatureFlagsModule.forRoot({
  flags: {
    'new-checkout': {
      enabled: true,
      percentage: 25, // 25% of users see this
    },
  },
});

User Targeting

const isEnabled = await featureFlags.isEnabled('premium-feature', {
  userId: 'user123',
  groups: ['premium', 'beta'],
});

A/B Testing

const variant = await featureFlags.getVariant('experiment-1', {
  userId: 'user123',
  variants: ['control', 'variant-a', 'variant-b'],
});

🎯 Use Cases

• Canary Releases - Roll out features gradually
• A/B Testing - Test different implementations
• Beta Programs - Limit features to beta users
• Kill Switches - Disable features instantly
• Scheduled Releases - Launch features at specific times

👤 Author

Alireza Aminzadeh

• Email: [email protected]
• GitHub: @syeedalireza
• NPM: @syeedalireza

📄 License

MIT License - see LICENSE file

Built with ❤️ for the NestJS community