Virtual List

Virtual List allows to render lists with huge amount of elements without loss of performance. And it is fully compatible with all Framework7 components which work with lists such as Search Bar, Infinite Scroll, Pull To Refresh, Swipeouts (swipe-to-delete) and Sortable.

Virtual List Layout

Virtual List HTML layout is pretty simple, it is almost the same as for usual List View with only difference: you need to leave it empty:

<!-- Virtual List -->
<div class="list virtual-list">
  <!-- keep it empty -->
</div>

Where:

virtual-list - required additional class on any list block that uses Virtual List

Virtual List App Methods

Now, when we have list's HTML, we need to initialize it. We need to use required App method:

app.virtualList.create(parameters)- initialize virtual list with parameters

parameters - object - object with virtual list parameters. Required.
Method returns initialized Virtual List instance

app.virtualList.destroy(el)- destroy Virtual List instance

el - HTMLElement or string (with CSS Selector) or object. Virtual List element or Virtual List instance to destroy.

app.virtualList.get(el)- get Virtual List instance by HTML element

el - HTMLElement or string (with CSS Selector). Virtual List element.

Method returns Virtual List's instance

Note that Virtual List container (list block element) should be in DOM on a moment of initialization.

Virtual List Parameters

Let's look on list of all available parameters:

Parameter	Type	Default	Description
el	HTMLElement string		Target List Block element. In case of `string` - CSS selector of list block element
ul	HTMLElement string		List element `<ul>` inside of List block.
createUl	boolean	true	Will automatically create `<ul>` element inside of Virtual List block. If disabled, then virtual list can be used on any block element without `ul > li` structure
items	array		Array with list items
rowsBefore	number		Amount of rows (items) to be rendered before current screen scroll position. By default it is equal to double amount of rows (items) that fit to screen
rowsAfter	number		Amount of rows (items) to be rendered after current screen scroll position. By default it is equal to the amount of rows (items) that fit to screen
cols	number	1	Number of items per row. Doesn't compatible when using Virtual List with dynamic height
height	number or function(item) or "auto"		If `number` - list item height in px. If `function` then function should return item height. By default equals to `44` for iOS theme, `48` for MD theme If `"auto"` it will calculate each item height automatically. It can work a bit slower in this case, but still much better when it is impossible to determine or predict item height
renderItem	function(item)		This optional function allows to use custom function to render item HTML. It could be used instead of template parameter
renderExternal	function(vl, renderParameters)		This optional function allows to render DOM items using some custom method. Useful in case it is used (e.g.) with Vue/React plugin to pass DOM rendering and manipulation to Vue/React. `renderParameters` conaints object with the following properties: `fromIndex`, `toIndex`, `listHeight`, `topPosition`, `items`
emptyTemplate	string		Defines list item template for the case if empty data passed
dynamicHeightBufferSize	number	1	This parameter allows to control buffer size on Virtual Lists with dynamic height (when `height` parameter is function) as a buffer size multiplier
cache	boolean	true	Disable or enable DOM cache for already rendered list items. In this case each item will be rendered only once and all further manipulations will be with DOM element. It is useful if your list items have some user interaction elements (like form elements or swipe outs) or could be modified
updatableScroll	boolean		Is the current device updates and handles scroll events during scroll. By default (if not specified) it is "false" for all iOS devices with iOS version less than 8.
setListHeight	boolean	true	Will set height on list block if enabled
showFilteredItemsOnly	boolean	false	Option to show filtered items only set by method
scrollableParentEl	HTMLElement string		Virtual list's scrollable parent. If not specified, then it will look for parent `<div class="page-content">` element
Searchbar
searchByItem	function(query, item, index)		Search function that will be used by Searchbar, it receives search query, item itself and item index. If item matches to search query you need to return `true`, otherwise this function should return `false`
searchAll	function(query, items)		Search function that will be used by Searchbar, it receives search query and array with all items. You need to loop through items and return array with indexes of matched items

Virtual List Methods & Properties

So to create Virtual List we have to call:

var virtualList = app.virtualList.create({ /* parameters */ })

After we initialize Virtual List we have its initialized instance in variable (like virtualList variable in example above) with helpful methods and properties:

Properties
virtualList.items	Array with items
virtualList.filteredItems	Array with filtered items (after using ".filterItems" method)
virtualList.domCache	Object with cached dom items
virtualList.params	Parameters passed on list initialization
virtualList.el	Virtual list target list block element
virtualList.$el	Dom7 instance of target list block element
virtualList.pageContentEl	Parent "page-content" element
virtualList.$pageContentEl	Dom7 instance of parent "page-content" element
virtualList.currentFromIndex	Index number of currently first rendered item
virtualList.currentToIndex	Index number of currently last rendered item
virtualList.reachEnd	Boolean property. Equals `true` if the currently last rendered item is the last item of all specified items
Methods
virtualList.filterItems(indexes);	Filter virtual list by passing array with indexes of items to show
virtualList.resetFilter();	Disable filter and display all items again
virtualList.appendItem(item);	Append item to virtual list
virtualList.appendItems(items);	Append array with items to virtual list
virtualList.prependItem(item);	Prepend item to virtual list
virtualList.prependItems(items);	Prepend array with items to virtual list
virtualList.replaceItem(index, item);	Replace item at specified index with the new one
virtualList.replaceAllItems(items);	Replace all items with arrays of new items
virtualList.moveItem(oldIndex, newIndex);	Move virtual item from oldIndex to newIndex
virtualList.insertItemBefore(index, item);	Insert new item before item with specified index
virtualList.deleteItem(index);	Delete item at specified index
virtualList.deleteItems(indexes);	Delete items at specified array of indexes
virtualList.deleteAllItems();	Delete all items
virtualList.clearCache();	Clear virtual list cached DOM elements
virtualList.destroy();	Destory initialized virtual list and detach all events
virtualList.update();	Update virtual list, including recalculation of list sizes and re-rendering of virtual list
virtualList.scrollToItem(index);	Scroll Virtual List to specified item by its index number

Virtual List Events

Virtual List will fire the following events on app and virtual list instance:

Virtual List instance emits events on both self instance and app instance. App instance events has same names prefixed with vl.

Event	Target	Arguments	Description
itemBeforeInsert	virtualList	virtualList, itemEl, item	Event will be triggered before item will be added to virtual document fragment
vlItemBeforeInsert	app	virtualList, itemEl, item
itemsBeforeInsert	virtualList	virtualList, fragment	Event will be triggered after current DOM list will be removed and before new document will be inserted
vlItemsBeforeInsert	app	virtualList, fragment
beforeClear	virtualList	virtualList, fragment	Event will be triggered before current DOM list will be removed and replaced with new document fragment
vlBeforeClear	app	virtualList, fragment
itemsAfterInsert	virtualList	virtualList, fragment	Event will be triggered after new document fragment with items inserted
vlItemsAfterInsert	app	virtualList, fragment

Examples

virtual-list.html

<template>
  <div class="page">
    <div class="navbar">
      <div class="navbar-bg"></div>
      <div class="navbar-inner sliding">
        <div class="title">Virtual List</div>
        <div class="subnavbar">
          <form data-search-container=".virtual-list" data-search-item="li" data-search-in=".item-title"
            class="searchbar searchbar-init">
            <div class="searchbar-inner">
              <div class="searchbar-input-wrap">
                <input type="search" placeholder="Search" />
                <i class="searchbar-icon"></i>
                <span class="input-clear-button"></span>
              </div>
              <span class="searchbar-disable-button">Cancel</span>
            </div>
          </form>
        </div>
      </div>
    </div>
    <div class="searchbar-backdrop"></div>
    <div class="page-content">
      <div class="block">
        <p>Virtual List allows to render lists with huge amount of elements without loss of performance. And it is fully
          compatible with all Framework7 list components such as Search Bar, Infinite Scroll, Pull To Refresh, Swipeouts
          (swipe-to-delete) and Sortable.</p>
        <p>Here is the example of virtual list with 10 000 items:</p>
      </div>
      <div class="list list-strong list-outline-ios inset-md list-dividers-ios links-list">
        <ul>
          <li>
            <a href="/virtual-list-vdom/">Virtual List VDOM</a>
          </li>
        </ul>
      </div>
      <div class="list list-strong list-outline-ios inset-md list-dividers-ios simple-list searchbar-not-found">
        <ul>
          <li>Nothing found</li>
        </ul>
      </div>
      <div class="list list-strong list-outline-ios inset-md list-dividers-ios virtual-list media-list searchbar-found">
      </div>
    </div>
  </div>
</template>
<script>
  export default (props, { $f7, $el, $theme, $onMounted, $onBeforeUnmount }) => {
    let items = [];
    let virtualList;
    for (let i = 1; i <= 10000; i++) {
      items.push({
        title: 'Item ' + i,
        subtitle: 'Subtitle ' + i
      });
    }
    $onMounted(() => {
      virtualList = $f7.virtualList.create({
        // List Element
        el: $el.value.find('.virtual-list'),
        // Pass array with items
        items,
        // Custom search function for searchbar
        searchAll: function (query, items) {
          var found = [];
          for (var i = 0; i < items.length; i++) {
            if (items[i].title.toLowerCase().indexOf(query.toLowerCase()) >= 0 || query.trim() === '') found.push(i);
          }
          return found; //return array with mathced indexes
        },
        // List item render
        renderItem(item) {
          return `
          <li>
            <a  class="item-link item-content">
              <div class="item-inner">
                <div class="item-title-row">
                  <div class="item-title">${item.title}</div>
                </div>
                <div class="item-subtitle">${item.subtitle}</div>
              </div>
            </a>
          </li>`;
        },
        // Item height
        height: $theme.ios ? 65 : 69,
      });
    });

    $onBeforeUnmount(() => {
      virtualList.destroy()
    });

    return $render;
  }
</script>

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On this page

Virtual List Layout
Virtual List App Methods
Virtual List Parameters
Virtual List Methods & Properties
Virtual List Events
Examples