loop.js

  startLoop = () => {
    this.loop = setInterval(this.someMethod, 5000)
  }

  clearLoop = () => {
    clearInterval(this.loop)
  }

  onFocus = () => {
    this.startLoop()
  }

  onBlur = () => {
    this.clearLoop()
  }
  
  addListeners = () => {
    window.addEventListener('focus', this.onFocus)
    window.addEventListener('blur', this.onBlur) 
  }