Function start

examples/06-custom-operators.js:21–98

()

const { Engine } = require('json-rules-engine')

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

  /**
   * Define a 'startsWith' custom operator, for use in later rules
   */
  engine.addOperator('startsWith', (factValue, jsonValue) => {
    if (!factValue.length) return false
    return factValue[0].toLowerCase() === jsonValue.toLowerCase()
  })

  /**
   * Add rule for detecting words that start with 'a'
   */
  const ruleA = {
    conditions: {
      all: [{
        fact: 'word',
        operator: 'startsWith',
        value: 'a'
      }]
    },
    event: {
      type: 'start-with-a'
    }
  }
  engine.addRule(ruleA)

  /*
  * Add rule for detecting words that start with 'b'
  */
  const ruleB = {
    conditions: {
      all: [{
        fact: 'word',
        operator: 'startsWith',
        value: 'b'
      }]
    },
    event: {
      type: 'start-with-b'
    }
  }
  engine.addRule(ruleB)

  // utility for printing output
  const printEventType = {
    'start-with-a': 'start with "a"',
    'start-with-b': 'start with "b"'
  }

  /**
   * Register listeners with the engine for rule success and failure
   */
  let facts