01-hello-world.mts

/*
 * This is the hello-world example from the README.
 *
 * Usage:
 *   node ./examples/01-hello-world.js
 *
 * For detailed output:
 *   DEBUG=json-rules-engine node ./examples/01-hello-world.js
 */

import "colors";
import { Engine } from "json-rules-engine";

async function start() {
  /**
   * Setup a new engine
   */
  const engine = new Engine();

  /**
   * Create a rule
   */
  engine.addRule({
    // define the 'conditions' for when "hello world" should display
    conditions: {
      all: [
        {
          fact: "displayMessage",
          operator: "equal",
          value: true,
        },
      ],
    },
    // define the 'event' that will fire when the condition evaluates truthy
    event: {
      type: "message",
      params: {
        data: "hello-world!",
      },
    },
  });

  /**
   * Define a 'displayMessage' as a constant value
   * Fact values do NOT need to be known at engine runtime; see the
   * 03-dynamic-facts.js example for how to pull in data asynchronously during runtime
   */
  const facts = { displayMessage: true };

  // engine.run() evaluates the rule using the facts provided
  const { events } = await engine.run(facts);

  events.map((event) => console.log(event.params!.data.green));
}

export default start();

/*
 * OUTPUT:
 *
 * hello-world!
 */