betweenMethods.js

const state = document.querySelector('#tweeningState');

document.querySelector('#playPauseButton')
  .addEventListener('click', toggle());

let between = new Between(0, 400)
  .time(2000)
  .on('pause', () => {
    state.innerText = 'state: paused';
  }).on('play', () => {
    state.innerText = 'state: running';
  });


function toggle() {
  if (between.isPaused) 
    between.play();
  else  
    between.pause();
}