old_contents: let curProject = 3
  const fadeTime = 600
  
  $(document).ready(() => {
    const projects = $('.showcase .project')
    $(projects[curProject]).fadeIn(fadeTime)
  
    // set up the click-event handlers
    $('.arrow-prev').click(() => {
      $(projects[curProject]).fadeOut(fadeTime, () => {
        // callback-function that enables crossfading between project-views
  
        curProject--
        if (curProject < 0) {
          // Only loop over actual projects
          curProject = projects.length - 1 // go to last
        }
        $(projects[curProject]).fadeIn(fadeTime)
      })
    })
  
    $('.arrow-next').click(() => {
      $(projects[curProject]).fadeOut(fadeTime, () => {
        // callback-function that enables crossfading between project-views
  
        curProject++
        if (curProject >= projects.length) {
          // only loop over actual projects
          curProject = 0 // go to first
        }
        $(projects[curProject]).fadeIn(fadeTime)
      })
    })
  })
  
new_contents: var curProject = 3
  var fadeTime = 600
  var projects
  
  $(document).ready(function () {
    projects = $('.showcase .project')
    $(projects[curProject]).fadeIn(fadeTime)
  
    // set up the click-event handlers
    $('.arrow-prev').click(function () {
      $(projects[curProject]).fadeOut(fadeTime, function () {
        // callback-function that enables crossfading between project-views
  
        curProject--
        if (curProject < 0) {
          // Only loop over actual projects
          curProject = projects.length - 1 // go to last
        }
        $(projects[curProject]).fadeIn(fadeTime)
      })
    })
  
    $('.arrow-next').click(function () {
      $(projects[curProject]).fadeOut(fadeTime, function () {
        // callback-function that enables crossfading between project-views
  
        curProject++
        if (curProject >= projects.length) {
          // only loop over actual projects
          curProject = 0 // go to first
        }
        $(projects[curProject]).fadeIn(fadeTime)
      })
    })
  })
  
subject: Rewrite showcase.js in ES5 for better mobile support.