Architecture

Understand Rule Engine in 2 minutes

The Core Idea

Rule Engine is like a judge:

• Rules = Laws to check
• Context = Evidence (your data)
• Engine = Judge who decides

// This is all you need to know
const rule = { gte: ['age', 18] };
const data = { age: 25 };

engine.evaluateExpr(rule, data);
// { success: true }

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Three Building Blocks

Block	What it does	Example
RuleEngine	Runs rules against data	engine.evaluateExpr(rule, data)
Operators	Logic building blocks	eq, and, contains, between
PathResolver	Safely reads nested values	'user.profile.age' → 25

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Optional: Stateful Engine

Need to track changes over time? Wrap with StatefulRuleEngine:

// Detect when temperature increases above 30
const rule = {
  and: [{ increased: ['temperature'] }, { gte: ['temperature', 30] }],
};

statefulEngine.on('triggered', (e) => {
  console.log('Alert! Temperature rising');
});

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What’s Next?

How It Works

Step-by-step evaluation flow

Internals

Deep dive for contributors