Revision 1077546 of IntersectionObserver

<p>{{SeeCompatTable}}{{APIRef("")}}</p>

<p>The <code><strong>IntersectionObserver</strong></code> interface of the the <a href="/en-US/docs/Web/API/Intersection_Observer_API">Intersection Observer API</a> provides a way to asynchronously observe changes in the intersection of a target element with an ancestor element or with a top-level document's {{Glossary('viewport')}}. The ancestor or viewport is referred to as the root.</p>

<h2 id="Constructor">Constructor</h2>

<dl>
 <dt>{{domxref("IntersectionObserver.IntersectionObserver()")}}</dt>
 <dd>Creates a new <code>IntersectionObserver</code> object.</dd>
</dl>

<h2 id="Properties">Properties</h2>

<dl>
 <dt>{{domxref("IntersectionObserver.root")}} {{readonlyinline}}</dt>
 <dd>A specific ancestor of the {{domxref("element")}} being observed. If no value was&nbsp;passed to the constructor, the top-level document's viewport is used.</dd>
 <dt>{{domxref("IntersectionObserver.rootMargin")}} {{readonlyinline}}</dt>
 <dd>An offset applied to the root's {{Glossary('bounding_box')}} when calculating intersections, effectively shrinking or growing the root for calculation purposes.&nbsp;This is not guaranteed to be identical to the value passed in the constructor. If no value was&nbsp;passed to the constructor, "0px 0px 0px 0px" is used. This property takes pixels ('px') or percentages ('%').</dd>
 <dt>{{domxref("IntersectionObserver.thresholds")}} {{readonlyinline}}</dt>
 <dd>A list of thresholds, sorted in increasing numeric order, where each threshold is a ratio of intersection area to bounding box area of an observed target. Notifications for a target are generated when any of the thresholds are crossed for that target. If no value was passed to the constructor, 0 is used.</dd>
</dl>

<h2 id="Methods">Methods</h2>

<dl>
 <dt>{{domxref("IntersectionObserver.disconnect")}}</dt>
 <dd>Stops the IntersectionObserver object from observing any target.</dd>
 <dt>{{domxref("IntersectionObserver.observe")}}</dt>
 <dd>Tells the <code>IntersectionObserver</code> a target element to observe.</dd>
 <dt>{{domxref("IntersectionObserver.takeRecords")}}</dt>
 <dd>Returns an array of {{domxref("IntersectionObserverEntry")}} objects for&nbsp;all observed targets and stops observing&nbsp;all of them.</dd>
 <dt>{{domxref("IntersectionObserver.unobserve")}}</dt>
 <dd>Tells the <code>IntersectionObserver</code> to stop observing a particular target element.</dd>
 <dt>
 <h2 id="Examples">Examples</h2>
 </dt>
</dl>

<pre class="brush: js">
<code data-lang="js">var intersectionObserver = new IntersectionObserver(function(entries) {
  // If intersectionRatio is 0, the target is out of view
  // and we do not need to do anything.
  if (entries[0].intersectionRatio &lt;= 0) {
    return;
  }
  loadItems(10);
  // appendChild will move the existing element, so there is no need to
  // remove it first.
  scroller.appendChild(target);
  loadItems(5);
  ChromeSamples.setStatus('Loaded up to item ' + counter);
});
intersectionObserver.observe(target);</code></pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('IntersectionObserver','#intersection-observer-private-slots','IntersectionObserver')}}</td>
   <td>{{Spec2('IntersectionObserver')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_Compatibility">Browser Compatibility</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari (WebKit)</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>
    <p>{{CompatChrome(51.0)}}</p>
   </td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Android Webview</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>Firefox OS</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
   <th>Chrome for Android</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatChrome(51.0)}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatChrome(51.0)}}</td>
  </tr>
 </tbody>
</table>
</div>