Lazy Load Collection List with Filters in Javascript

Lazy loading is a technique used to defer the loading of resources (such as images or videos) until they are actually needed by the user. This can be useful for improving the performance of a website or web application, especially on mobile devices or slow internet connections.

In the context of a collection list with filters, lazy loading can be implemented by only loading a portion of the collection at a time and then loading more items as the user scrolls down the page. Additionally, the filtering functionality can be implemented by only displaying items that match the selected filters, rather than loading all items at once.

Here is an example of how to implement lazy loading and filtering in JavaScript:

// Initialize an array to store the collection
let collection = [];
// Set the number of items to load per "page"
let itemsPerPage = 10;
// Initialize the current page and filter
let currentPage = 0;
let currentFilter = "all";
// Function to load the next page of items
function loadNextPage() {
  let startIndex = currentPage * itemsPerPage;
  let endIndex = startIndex + itemsPerPage;
  let itemsToLoad = collection.slice(startIndex, endIndex);
  // Do something with the items (e.g. add them to the DOM)
  for (let item of itemsToLoad) {
    let itemElem = document.createElement("div");
    itemElem.innerHTML = item;
// Function to apply a filter
function applyFilter(filter) {
  currentFilter = filter;
  currentPage = 0;
  document.getElementById("collection-list").innerHTML = "";
// Event listener to load the next page when the user scrolls
document.addEventListener("scroll", function() {
  if (window.innerHeight + window.scrollY >= document.body.offsetHeight) {

You can adjust the logic of loading item based on your requirements.

Advantages of Lazy Loading

Lazy loading has several advantages that can improve the performance and user experience of a website or web application. Some of the main advantages of lazy loading include:

It is important to note that lazy loading is not always the best solution for every use case and that is depends on the type of resources, the user's network conditions, and other factors.

Disadvantages of Lazy Loading

While lazy loading can offer many benefits, it also has some potential disadvantages that you should be aware of:

It is important to weigh these disadvantages against the potential benefits of lazy loading for your specific use case and to implement it carefully. There are also other optimization techniques to improve page loading performance like code splitting, preloading, compressing etc.