index.js

const gpio = require('onoff').Gpio

const red = new gpio(9, 'out')
const yellow = new gpio(10, 'out')
const green = new gpio(11, 'out')

const sleep = (howLong) => { 
  return new Promise((resolve) => {
    setTimeout(resolve, howLong)
  })
}

const runLights = async () => {
  while (true) {
    // Red
    red.writeSync(1)
    await sleep(3000)

    // Red and Yellow
    yellow.writeSync(1)
    await sleep(1000)

    // Green
    red.writeSync(0)
    yellow.writeSync(0)
    green.writeSync(1)
    await sleep(5000)

    // Yellow
    green.writeSync(0)
    yellow.writeSync(1)
    await sleep(2000)

    // Yellow off
    yellow.writeSync(0)
  }
}

const allLightsOff = () => {
  red.writeSync(0)
  yellow.writeSync(0)
  green.writeSync(0)
}

// Handle Ctrl+C exit cleanly 
process.on('SIGINT', () => {
  allLightsOff()
  process.exit()
})

allLightsOff()
runLights()