feature-flag-manager

Deploy features safely. Toggle on/off instantly, run A/B tests, and roll out gradually from 1% to 100% — no code redeployment needed.

What It Does

Control feature visibility in real-time without pushing new code:

• Instant toggle — Enable/disable features with one command
• Gradual rollout — Start with 1% of users, increase slowly
• A/B testing — Test variants against each other with automatic traffic splitting
• Kill switch — Emergency off button for buggy features
• User targeting — Show features to specific users or groups

Quick Start

# 1. Create a feature flag
node flag.js create dark-mode --description "Dark theme UI"

# 2. Enable for 10% of users
node flag.js update dark-mode --percentage 10

# 3. Check if enabled for current user
node flag.js enabled dark-mode --user-id alice
# → true (or false based on percentage)

# 4. Gradually increase to 100%
node flag.js update dark-mode --percentage 50
node flag.js update dark-mode --percentage 100

Common Use Cases

🚀 Safe Feature Releases

# Instead of: deploy → pray → rollback
# Do this: deploy (disabled) → enable 5% → monitor → 25% → 100%

node flag.js create new-checkout-flow
node flag.js update new-checkout-flow --percentage 5
# Monitor error rates...
node flag.js update new-checkout-flow --percentage 100

🧪 A/B Test Pricing Pages

# Test 3 variants: 50% see current, 25% see v1, 25% see v2
node flag.js create pricing-test --variants control,v1,v2 --weights 50,25,25

# In your code, get variant for each user
node flag.js variant pricing-test --user-id user123
# → "v1"

🚨 Emergency Kill Switch

# New feature causing errors? Disable instantly without redeploying
node flag.js toggle broken-feature --off
# Fixed? Re-enable
node flag.js toggle broken-feature --on

All Commands

Configuration

Flags stored in .featureflags/config.json:

{
  "flags": {
    "dark-mode": {
      "enabled": true,
      "percentage": 25,
      "description": "Dark theme support"
    },
    "pricing-test": {
      "enabled": true,
      "percentage": 100,
      "variants": ["control", "v1", "v2"],
      "weights": [50, 25, 25]
    }
  }
}

Integration Example

const flag = require('./flag.js');

async function renderDashboard(userId) {
  // Check if new dashboard is enabled for this user
  if (await flag.enabled('new-dashboard', { userId })) {
    return renderNewDashboard();
  }
  return renderLegacyDashboard();
}