arvarus's basic rules engine

This is a basic rules engine that can be used to evaluate rules and set a result.

Golden rules

• The evaluate function must return a boolean

• The evaluate function must not change the context

• The evaluate function must not change the results

• The action function must not change the context

• The action function must not change the results

• The action function must return a partial result

• The rules are evaluated in the order they are added

• The rules are evaluated until the first rule that returns true

Usage

const ruleEngine = new RuleEngine(context, rules, initialResult);

await ruleEngine.run()

console.log(ruleEngine.getResult());

Example

import RuleEngine from '@arvarus/basic-rules-engine';

const context = { startValue: 0, endValue: 3 };
const initialResult = {};

const rules = [
  {
    name: 'Init result',
    evaluate: async (context, result) => result.count == undefined,
    action: async (context) =>
      Promise.resolve({ count: context.startValue, flag: false }),
  },
  {
    name: 'Increment count when less than 3',
    evaluate: async (context, result) =>
      Promise.resolve(result.flag !== true && (result.count ?? 0) < context.endValue),
    action: async (context, result) =>
      Promise.resolve({ count: (result.count ?? 0) + 1 }),
  },
  {
    name: 'Set flag when count equals 3',
    evaluate: async (context, result) =>
      Promise.resolve(result.count === context.endValue && !result.flag),
    action: async () => Promise.resolve({ flag: true }),
  },
];

const ruleEngine = new RuleEngine(context, rules, initialResult);

await ruleEngine.run()

console.log(ruleEngine.getResult());
// { count: 3, flag: true }

Next Steps

• Add examples
• Add documentation
• Handle errors in evaluation or actions

History

• 2.0.x: (Breaking change)
  • run function now returns the result
• 1.0.x: Initial version