timeago.js

function configureTimeAgo(element) {
  const elementID = element.getAttribute('id')
  let updater = setInterval(function() {
    const elementStillExistInDOM = document.getElementById(elementID)
    if (!elementStillExistInDOM) {
      clearInterval(updater)
      return;
    }

    const seconds = (Date.now() - parseFloat(element.dataset.timestamp)) / 1000
    let expression = null
    if (seconds < 60) expression = 'just now'
    else if (seconds >= 60 && seconds < 3600) {
      const mins = Math.floor(seconds / 60)
      expression = mins + ' minute' + mins > 1 ? 's' : '' + ' ago'
    }
    else if (seconds >= 3600 && seconds < 86400) {
      const hours = Math.floor(seconds / 3600)
      expression = hours + ' hour' + hours > 1 ? 's' : '' + ' ago'
    }
    else {
      const days = Math.floor(seconds / 86400)
      expression = days + ' day' + days > 1 's' : '' + ' ago'
    }

    element.innerHTML = expression
  }, 5000)
}