<!-- 由官方 Demo 中抽取出  -->
<!-- https://haltu.github.io/muuri/ -->

<section class="grid-demo">

      <h2 class="section-title"><span>Grid Demo</span></h2>

      <div class="controls cf">
        <div class="control search">
          <div class="control-icon">
            <i class="material-icons">&#xE8B6;</i>
          </div>
          <input class="control-field search-field form-control " type="text" name="search" placeholder="Search..." />
        </div>
        <div class="control filter">
          <div class="control-icon">
            <i class="material-icons">&#xE152;</i>
          </div>
          <div class="select-arrow">
            <i class="material-icons">&#xE313;</i>
          </div>
          <select class="control-field filter-field form-control">
            <option value="" selected>All</option>
            <option value="red">Red</option>
            <option value="blue">Blue</option>
            <option value="green">Green</option>
          </select>
        </div>
        <div class="control sort">
          <div class="control-icon">
            <i class="material-icons">&#xE164;</i>
          </div>
          <div class="select-arrow">
            <i class="material-icons">&#xE313;</i>
          </div>
          <select class="control-field sort-field form-control">
            <option value="order" selected>Drag</option>
            <option value="title">Title (drag disabled)</option>
            <option value="color">Color (drag disabled)</option>
          </select>
        </div>
        <div class="control layout">
          <div class="control-icon">
            <i class="material-icons">&#xE871;</i>
          </div>
          <div class="select-arrow">
            <i class="material-icons">&#xE313;</i>
          </div>
          <select class="control-field layout-field form-control">
            <option value="left-top" selected>Left Top</option>
            <option value="left-top-fillgaps">Left Top (fill gaps)</option>
            <option value="right-top">Right Top</option>
            <option value="right-top-fillgaps">Right Top (fill gaps)</option>
            <option value="left-bottom">Left Bottom</option>
            <option value="left-bottom-fillgaps">Left Bottom (fill gaps)</option>
            <option value="right-bottom">Right Bottom</option>
            <option value="right-bottom-fillgaps">Right Bottom (fill gaps)</option>
          </select>
        </div>
      </div>

      <div class="grid"></div>

      <div class="grid-footer">
        <button class="add-more-items btn btn-primary"><i class="material-icons">&#xE145;</i>Add more items</button>
      </div>

</section>

/* demo-grid.css */
/* Controls */

.controls {
  margin: 30px -10px;
}
.control {
  position: relative;
  float: left;
  width: 25%;
  padding: 0 10px;
}
@media (max-width: 600px) {
  .control {
    float: none;
    width: auto;
    margin: 0 0 15px 0;
  }
  .control.layout {
    margin: 0;
  }
}
.control-icon {
  position: absolute;
  left: 10px;
  top: 0;
  width: 40px;
  height: 40px;
  line-height: 40px;
  text-align: center;
  z-index: 2;
  pointer-events: none;
}
.control-field {
  position: relative;
  padding-left: 40px;
  z-index: 1;
}

/* Grid */

.grid {
  position: relative;
  max-width: 960px;
  margin: 0 -10px;
  -moz-box-sizing: content-box;
  -webkit-box-sizing: content-box;
  box-sizing: content-box;
}
.item {
  position: absolute;
  width: 100px;
  height: 100px;
  line-height: 100px;
  margin: 10px;
  z-index: 1;
  will-change: transform;
}
.item.muuri-item-positioning {
  z-index: 2;
}
.item.muuri-item-dragging,
.item.muuri-item-releasing {
  z-index: 9999;
}
.item.muuri-item-dragging {
  cursor: move;
}
.item.muuri-item-hidden {
  z-index: 0;
}
.item.h2 {
  height: 220px;
  line-height: 220px;
}
.item.w2 {
  width: 220px;
}
.item-content {
  position: relative;
  width: 100%;
  height: 100%;
}
.card {
  position: absolute;
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
  text-align: center;
  font-size: 24px;
  font-weight: 300;
  background-color: rgba(255,255,255,0.9);
  border: 2px solid;
  color: #333;
  border-radius: 4px;
  -webkit-transition: all 0.2s ease-out;
  -moz-transition: all 0.2s ease-out;
  -ms-transition: all 0.2s ease-out;
  -o-transition: all 0.2s ease-out;
  transition: all 0.2s ease-out;
}
.item.red .card {
  color: #f94a7a;
}
.item.green .card {
  color: #2ac06d;
}
.item.blue .card {
  color: #4A9FF9;
}
.card-id {
  position: absolute;
  left: 7px;
  top: 0;
  height: 30px;
  line-height: 30px;
  text-align: left;
  font-size: 16px;
  font-weight: 400;
}
.card-remove {
  position: absolute;
  right: 0;
  top: 0;
  width: 30px;
  height: 30px;
  line-height: 30px;
  text-align: center;
  font-size: 20px;
  font-weight: 400;
  cursor: pointer;
  -moz-transform: scale(0);
  -webkit-transform: scale(0);
  -o-transform: scale(0);
  -ms-transform: scale(0);
  transform: scale(0);
  -webkit-transition: all 0.15s ease-out;
  -moz-transition: all 0.15s ease-out;
  -ms-transition: all 0.15s ease-out;
  -o-transition: all 0.15s ease-out;
  transition: all 0.15s ease-out;
}
.card:hover > .card-remove {
  -moz-transform: scale(1);
  -webkit-transform: scale(1);
  -o-transform: scale(1);
  -ms-transform: scale(1);
  transform: scale(1);
}

/* Grid Footer */

.grid-footer {
  margin: 60px 0;
  text-align: center;
}
.grid-footer .btn .material-icons {
  margin-right: 10px;
  font-size: 24px;
}



/* Icons in the selector */
/* fallback */
@font-face {
  font-family: 'Material Icons';
  font-style: normal;
  font-weight: 400;
  src: url(https://fonts.gstatic.com/s/materialicons/v29/2fcrYFNaTjcS6g4U3t-Y5ZjZjT5FdEJ140U2DJYC3mY.woff2) format('woff2');
}

.material-icons {
  font-family: 'Material Icons';
  font-weight: normal;
  font-style: normal;
  font-size: 24px;
  line-height: 1;
  letter-spacing: normal;
  text-transform: none;
  display: inline-block;
  white-space: nowrap;
  word-wrap: normal;
  direction: ltr;
  -webkit-font-feature-settings: 'liga';
  -webkit-font-smoothing: antialiased;
}



/* main.css */
/* Base */

* {
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}
html {
  overflow-y: scroll;
  overflow-x: hidden;
  background: #fff;
}
html.dragging body {
  -moz-user-select: none;
  -webkit-user-select: none;
  -ms-user-select: none;
  user-select: none;
}
body {
  position: relative;
  font-family: 'Fira Sans', Helvetica, Arial, sans-serif;
  font-size: 18px;
  line-height: 1.5;
  margin: 0 20px;
  color: #6e6e6e;
}
a {
  color: #3396FF;
  text-decoration: none;
  -webkit-transition: all 0.2s ease-out;
  -moz-transition: all 0.2s ease-out;
  -ms-transition: all 0.2s ease-out;
  -o-transition: all 0.2s ease-out;
  transition: all 0.2s ease-out;
}
a:hover {
  color: #FF4BD8;
}

/* Clearfix */

.cf:before,
.cf:after {
  content: " ";
  display: table;
}
.cf:after {
  clear: both;
}

/* Material icons */

.material-icons {
  display: inline-block;
  vertical-align: top;
  line-height: inherit;
  font-size: inherit;
}

/* Buttons */

.btn {
  display: inline-block;
  position: relative;
  vertical-align: top;
  margin: 0;
  border: 0;
  outline: 0;
  padding: 0px 15px;
  font-size: 16px;
  font-weight: 400;
  line-height: 40px;
  height: 40px;
  text-align: center;
  white-space: nowrap;
  background: #4a9ff9;
  color: #fff;
  -ms-touch-action: manipulation;
  touch-action: manipulation;
  cursor: pointer;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
  border-radius: 3px;
}
.btn:focus,
.btn:hover,
.btn:active {
  outline: 0;
}
.btn:hover {
  background: #3989de;
}
.btn:active {
  background: #3075bf;
}
.btn.active {
  background: #60ca47;
}
.btn.active:hover {
  background: #40b325;
}
.btn.active:active {
  background: #309818;
}

/* Forms */

.form-control {
  display: block;
  width: 100%;
  height: 40px;
  padding: 5px 15px;
  font-size: 16px;
  line-height: 26px;
  color: inherit;
  background: #fff;
  border: 2px solid #e5e5e5;
  border-radius: 4px;
  -webkit-appearance: none;
  -moz-appearance: none;
  -o-appearance: none;
  appearance: none;
}
select.form-control {
  padding-right: 40px;
  cursor: pointer;
}
select.form-control::-ms-expand {
  display: none;
}
.select-arrow {
  position: absolute;
  right: 10px;
  top: 0;
  width: 40px;
  height: 40px;
  line-height: 40px;
  text-align: center;
  z-index: 2;
  pointer-events: none;
}
.form-control:focus {
  outline: 0;
  border-color: #4a9ff9;
}

/* Header */

header {
  margin: 30px auto;
  max-width: 940px;
}
header .logo {
  max-width: 240px;
  margin: 60px auto 60px auto;
}
header .logo svg {
  width: 100%;
  height: 100%;
}
header h1 {
  display: none;
}
header h2 {
  text-align: center;
  font-size: 24px;
  line-height: 1.5;
  font-weight: 400;
  max-width: 940px;
  margin: 0 auto;
  color: #6e6e6e;
}
header h2 > span {
  display: block;
  font-size: 18px;
  color: #aaa;
  margin-top: 3px;
}
header h2 > span > i {
  margin: 0 10px;
  color: #ccc;
}
header aside {
  color: #bbb;
  font-size: 15px;
  margin-top: 5px;
  font-style: italic;
  text-align: center;
}
header nav {
  text-align: center;
}
header nav a {
  position: relative;
  display: inline-block;
  vertical-align: top;
  position: relative;
  padding: 20px;
  font-size: 20px;
  font-weight: 400;
}
header nav a i {
  display: block;
  position: absolute;
  height: 2px;
  bottom: 20px;
  left: 20px;
  right: 20px;
  background-color: #FF4BD8;
  opacity: 0;
  z-index: 2;
  -moz-transform: scale(0, 1);
  -webkit-transform: scale(0, 1);
  -o-transform: scale(0, 1);
  -ms-transform: scale(0, 1);
  transform: scale(0, 1);
  -webkit-transition: -webkit-transform 0.2s ease-out, opacity 0s ease 0.2s;
  -moz-transition: -moz-transform 0.2s ease-out, opacity 0s ease 0.2s;
  -ms-transition: -ms-transform 0.2s ease-out, opacity 0s ease 0.2s;
  -o-transition: -o-transform 0.2s ease-out, opacity 0s ease 0.2s;
  transition: transform 0.2s ease-out, opacity 0s ease 0.2s;
}
header nav a:hover i {
  opacity: 1;
  -moz-transform: scale(1, 1);
  -webkit-transform: scale(1, 1);
  -o-transform: scale(1, 1);
  -ms-transform: scale(1, 1);
  transform: scale(1, 1);
  -webkit-transition: -webkit-transform 0.2s ease-out, opacity 0s ease 0s;
  -moz-transition: -moz-transform 0.2s ease-out, opacity 0s ease 0s;
  -ms-transition: -ms-transform 0.2s ease-out, opacity 0s ease 0s;
  -o-transition: -o-transform 0.2s ease-out, opacity 0s ease 0s;
  transition: transform 0.2s ease-out, opacity 0s ease 0s;
}
@media (max-width: 600px) {
  header {
    margin-bottom: 0;
  }
  header h2 {
    font-size: 21px;
  }
  header h2 > span {
    margin-top: 20px;
  }
  header h2 > span > i {
    display: none;
  }
  header h2 > span > span {
    display: block;
  }
  header nav {
    margin-top: 20px;
    border-bottom: 0;
    border-top: 1px solid #e5e5e5;
  }
  header nav a {
    display: block;
    vertical-align: top;
    padding: 10px 20px;
    border-bottom: 1px solid #e5e5e5;
  }
  header nav a i {
    bottom: -1px;
    left: 0;
    right: 0;
  }
}

/* Footer */

footer {
  margin: 0 auto;
  max-width: 940px;
  text-align: center;
  border-top: 2px solid #e5e5e5;
  padding-top: 30px;
  padding-bottom: 30px;
}
footer p {
  margin: 0;
}
footer .credits {
  color: #aaa;
  margin-bottom: 5px;
  font-style: italic;
}
footer .copyright i {
  font-size: 24px;
  height: 27px;
  line-height: 32px;
  display: inline-block;
  vertical-align: top;
}

/* Sections */

section {
  margin: 60px auto;
  padding-top: 0;
  max-width: 940px;
  border-top: 2px solid #e5e5e5;
  text-align: left;
}
section.demo {
  margin-top: 30px;
}
section h4 {
  margin: 30px 0 15px 0;
  font-weight: 500;
  font-size: 20px;
  color: #3e3e3e;
}
@media (max-width: 600px) {
  section.demo {
    border-top: 0;
  }
}

/* Section titles */

.section-title {
  color: #3e3e3e;
  font-size: 26px;
  font-weight: 700;
  margin: 40px 0;
  letter-spacing: 2px;
  text-transform: uppercase;
  text-align: center;
}
.section-title > span {
  position: relative;
  display: inline-block;
  vertical-align: top;
}
.section-title > span:after {
  content: "";
  display: block;
  position: absolute;
  left: 10px;
  bottom: 0;
  right: 10px;
  height: 2px;
  background: #3e3e3e;
}

/* Feature list */

.feature-list {
  margin: 0;
  padding: 0;
  list-style: none;
}
.feature-list-item {
  position: relative;
  padding-left: 80px;
  margin: 30px 0;
  overflow: hidden;
}
.feature-list-icon {
  display: block;
  float: left;
  margin-left: -80px;
  width: 80px;
  font-size: 48px;
  line-height: 48px;
  text-align: left;
  color: #3396FF;
}
.feature-list-text h4 {
  margin: 0 0 15px 0;
  font-weight: 500;
  font-size: 20px;
}
@media (max-width: 600px) {
  .feature-list-item {
    padding-left: 0;
  }
  .feature-list-icon {
    margin: -4px 10px 0 0;
    width: 24px;
    font-size: 24px;
    line-height: inherit;
  }
}

/* Author */

.author {
  margin: 60px 0;
  font-weight: 500;
  font-size: 20px;
  color: #3e3e3e;
  font-style: italic;
  text-align: center;
}

/* 由 demo-grid.css 取出再覆蓋執行一次 */
.control-field {
    position: relative;
    padding-left: 40px;
    z-index: 1;
}

document.addEventListener('DOMContentLoaded', function () {

  //
  // Initialize stuff
  // 初始化物件，宣告一堆變數。
  //

  var grid = null;
  var docElem = document.documentElement;
  var demo = document.querySelector('.grid-demo');
  var gridElement = demo.querySelector('.grid');
  var filterField = demo.querySelector('.filter-field');
  var searchField = demo.querySelector('.search-field');
  var sortField = demo.querySelector('.sort-field');
  var layoutField = demo.querySelector('.layout-field');
  var addItemsElement = demo.querySelector('.add-more-items');
  var characters = 'abcdefghijklmnopqrstuvwxyz';
  var filterOptions = ['red', 'blue', 'green'];
  var dragOrder = [];
  var uuid = 0;
  var filterFieldValue;
  var sortFieldValue;
  var layoutFieldValue;
  var searchFieldValue;

  //
  // Grid helper functions
  //

  function initDemo() {

    initGrid();

    // Reset field values.
    searchField.value = '';
    [sortField, filterField, layoutField].forEach(function (field) {
      field.value = field.querySelectorAll('option')[0].value;
    });

    // Set inital search query, active filter, active sort value and active layout.
    searchFieldValue = searchField.value.toLowerCase();
    filterFieldValue = filterField.value;
    sortFieldValue = sortField.value;
    layoutFieldValue = layoutField.value;

    // Search field binding.
    searchField.addEventListener('keyup', function () {
      var newSearch = searchField.value.toLowerCase();
      if (searchFieldValue !== newSearch) {
        searchFieldValue = newSearch;
        filter();
      }
    });

    // Filter, sort and layout bindings.
    filterField.addEventListener('change', filter);
    sortField.addEventListener('change', sort);
    layoutField.addEventListener('change', changeLayout);

    // Add/remove items bindings.
    addItemsElement.addEventListener('click', addItems);
    gridElement.addEventListener('click', function (e) {
      if (elementMatches(e.target, '.card-remove, .card-remove i')) {
        removeItem(e);
      }
    });

  }

  function initGrid() {

    var dragCounter = 0;

    grid = new Muuri(gridElement, {
      items: generateElements(20),
      layoutDuration: 400,
      layoutEasing: 'ease',
      dragEnabled: true,
      dragSortInterval: 50,
      dragContainer: document.body,
      dragStartPredicate: function (item, event) {
        var isDraggable = sortFieldValue === 'order';
        var isRemoveAction = elementMatches(event.target, '.card-remove, .card-remove i');
        return isDraggable && !isRemoveAction ? Muuri.ItemDrag.defaultStartPredicate(item, event) : false;
      },
      dragReleaseDuration: 400,
      dragReleseEasing: 'ease'
    })
    .on('dragStart', function () {
      ++dragCounter;
      docElem.classList.add('dragging');
    })
    .on('dragEnd', function () {
      if (--dragCounter < 1) {
        docElem.classList.remove('dragging');
      }
    })
    .on('move', updateIndices)
    .on('sort', updateIndices);

  }

  function filter() {

    filterFieldValue = filterField.value;
    grid.filter(function (item) {
      var element = item.getElement();
      var isSearchMatch = !searchFieldValue ? true : (element.getAttribute('data-title') || '').toLowerCase().indexOf(searchFieldValue) > -1;
      var isFilterMatch = !filterFieldValue ? true : (element.getAttribute('data-color') || '') === filterFieldValue;
      return isSearchMatch && isFilterMatch;
    });

  }

  function sort() {

    // Do nothing if sort value did not change.
    var currentSort = sortField.value;
    if (sortFieldValue === currentSort) {
      return;
    }

    // If we are changing from "order" sorting to something else
    // let's store the drag order.
    if (sortFieldValue === 'order') {
      dragOrder = grid.getItems();
    }

    // Sort the items.
    grid.sort(
      currentSort === 'title' ? compareItemTitle :
      currentSort === 'color' ? compareItemColor :
      dragOrder
    );

    // Update indices and active sort value.
    updateIndices();
    sortFieldValue = currentSort;

  }

  function addItems() {

    // Generate new elements.
    var newElems = generateElements(5);

    // Set the display of the new elements to "none" so it will be hidden by
    // default.
    newElems.forEach(function (item) {
      item.style.display = 'none';
    });

    // Add the elements to the grid.
    var newItems = grid.add(newElems);

    // Update UI indices.
    updateIndices();

    // Sort the items only if the drag sorting is not active.
    if (sortFieldValue !== 'order') {
      grid.sort(sortFieldValue === 'title' ? compareItemTitle : compareItemColor);
      dragOrder = dragOrder.concat(newItems);
    }

    // Finally filter the items.
    filter();

  }

  function removeItem(e) {

    var elem = elementClosest(e.target, '.item');
    grid.hide(elem, {onFinish: function (items) {
      var item = items[0];
      grid.remove(item, {removeElements: true});
      if (sortFieldValue !== 'order') {
        var itemIndex = dragOrder.indexOf(item);
        if (itemIndex > -1) {
          dragOrder.splice(itemIndex, 1);
        }
      }
    }});
    updateIndices();

  }

  function changeLayout() {

    layoutFieldValue = layoutField.value;
    grid._settings.layout = {
      horizontal: false,
      alignRight: layoutFieldValue.indexOf('right') > -1,
      alignBottom: layoutFieldValue.indexOf('bottom') > -1,
      fillGaps: layoutFieldValue.indexOf('fillgaps') > -1
    };
    grid.layout();

  }

  //
  // Generic helper functions
  //

  function generateElements(amount) {

    var ret = [];

    for (var i = 0, len = amount || 1; i < amount; i++) {

      var id = ++uuid;
      var color = getRandomItem(filterOptions);
      var title = generateRandomWord(2);
      var width = Math.floor(Math.random() * 2) + 1;
      var height = Math.floor(Math.random() * 2) + 1;
      var itemElem = document.createElement('div');
      var itemTemplate = '' +
          '<div class="item h' + height + ' w' + width + ' ' + color + '" data-id="' + id + '" data-color="' + color + '" data-title="' + title + '">' +
            '<div class="item-content">' +
              '<div class="card">' +
                '<div class="card-id">' + id + '</div>' +
                '<div class="card-title">' + title + '</div>' +
                '<div class="card-remove"><i class="material-icons">&#xE5CD;</i></div>' +
              '</div>' +
            '</div>' +
          '</div>';

      itemElem.innerHTML = itemTemplate;
      ret.push(itemElem.firstChild);

    }

    return ret;

  }

  function getRandomItem(collection) {

    return collection[Math.floor(Math.random() * collection.length)];

  }

  function generateRandomWord(length) {

    var ret = '';
    for (var i = 0; i < length; i++) {
      ret += getRandomItem(characters);
    }
    return ret;

  }

  function compareItemTitle(a, b) {

    var aVal = a.getElement().getAttribute('data-title') || '';
    var bVal = b.getElement().getAttribute('data-title') || '';
    return aVal < bVal ? -1 : aVal > bVal ? 1 : 0;

  }

  function compareItemColor(a, b) {

    var aVal = a.getElement().getAttribute('data-color') || '';
    var bVal = b.getElement().getAttribute('data-color') || '';
    return aVal < bVal ? -1 : aVal > bVal ? 1 : compareItemTitle(a, b);

  }

  function updateIndices() {

    grid.getItems().forEach(function (item, i) {
      item.getElement().setAttribute('data-id', i + 1);
      item.getElement().querySelector('.card-id').innerHTML = i + 1;
    });

  }

  function elementMatches(element, selector) {

    var p = Element.prototype;
    return (p.matches || p.matchesSelector || p.webkitMatchesSelector || p.mozMatchesSelector || p.msMatchesSelector || p.oMatchesSelector).call(element, selector);

  }

  function elementClosest(element, selector) {

    if (window.Element && !Element.prototype.closest) {
      var isMatch = elementMatches(element, selector);
      while (!isMatch && element && element !== document) {
        element = element.parentNode;
        isMatch = element && element !== document && elementMatches(element, selector);
      }
      return element && element !== document ? element : null;
    }
    else {
      return element.closest(selector);
    }

  }

  //
  // Fire it up!
  //

  initDemo();

});