| <!DOCTYPE html> |
| <head> |
| <title>Images with loading='lazy' load only when in the viewport</title> |
| <link rel="author" title="Scott Little" href="mailto:[email protected]"> |
| <link rel="author" title="Dom Farolino" href="mailto:[email protected]"> |
| <link rel="help" href="https://github.com/scott-little/lazyload"> |
| <script src="/resources/testharness.js"></script> |
| <script src="/resources/testharnessreport.js"></script> |
| </head> |
| |
| <script> |
| const t = async_test("Images with loading='lazy' load only when in the viewport"); |
| |
| let has_in_viewport_loaded = false; |
| let has_window_load_fired = false; |
| |
| const in_viewport_img_onload = t.step_func(() => { |
| assert_false(has_in_viewport_loaded, |
| "The in_viewport element should load only once."); |
| has_in_viewport_loaded = true; |
| assert_true(document.getElementById("in_viewport").complete); |
| document.getElementById("below_viewport").scrollIntoView(); |
| }); |
| |
| window.addEventListener("load", t.step_func(() => { |
| has_window_load_fired = true; |
| })); |
| |
| const below_viewport_img_onload = t.step_func_done(() => { |
| assert_true(has_in_viewport_loaded, |
| "The below-viewport image should not load until it has been " + |
| "scrolled into viewport, after the in-viewport image loads"); |
| assert_true(has_window_load_fired, |
| "Below-viewport loading=lazy images should not block the " + |
| "window load event from firing"); |
| }); |
| </script> |
| |
| <body> |
| <!-- |in_viewport| takes 2 seconds to load, so that in browsers that don't |
| support lazy loading, |below_viewport| finishes before |in_viewport|, and |
| the test will dependably fail without relying on a timeout. --> |
| <img id="in_viewport" loading="lazy" src="resources/image.png?first&pipe=trickle(d2)" |
| onload="in_viewport_img_onload();"> |
| <div style="height:1000vh;"></div> |
| <img id="below_viewport" loading="lazy" src="resources/image.png?second" |
| onload="below_viewport_img_onload();"> |
| </body> |
