(function () {
  var d3 = window.d3
  // have a reference to the containing element
  var dom = d3.select('.js-vis-wrap')
  // create some dummy data
  /* const data = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 ...] */
  var data = d3.range(14).map(function (n) { return n * 10; })
  // have a max number of items to display
  var maxDisplay = 6
  // track if the pagination is clicked
  var paginationState = true
  // labels for pagination button
  var paginationText = ['next  →', '← prev']

  // loop through the data to append charts
  data.forEach(function (d, i) {
    console.log(d)
    // put max number of items in this div
    if (i < maxDisplay) {
      createChart(d, i, '.js-vis-1')
    } else {
    // overflow any others here
      createChart(d, i, '.js-vis-2')
    }
  })

  // add pagination if over max number of items
  if (data.length > maxDisplay) {
    createPagination(dom)
  } else {
    removePagination(dom)
  }

  // create a simple 'chart' to illustrate example
  function createChart (datum, index, selection) {
    // this could be an svg etc
    dom.select(selection).append('div')
      .attr('class', 'col col-2 p2 m1 chart i-' + index)
      .append('h1')
      .attr('class', 'center')
      .text(datum)
  }
  // add pagination
  function createPagination (sel) {
    sel.append('button')
      .attr('class', 'pagination inline-block btn btn-primary m1')
      .on('click', function () {
        // main div holding 9 items
        sel.select('.js-vis-1')
          .classed('display-none', paginationState)
        // div holding remaining items
        sel.select('.js-vis-2')
          .classed('display-none', !paginationState)
        // update pagination state
        if (paginationState) {
          paginationState = false
          // update the btn label 'prev'
          sel.select('.pagination')
            .text(paginationText[1])
        } else {
          paginationState = true
          // update the btn label 'next'
          sel.select('.pagination')
            .text(paginationText[0])
        }
      })
      .text(paginationText[0])
  }
  // have a method to clear pagination when not needed
  function removePagination (sel) {
    sel.select('.pagination').remove()
  }
}())