{"json_modified": "2016-08-11T15:14:09.234457", "uuid": "8e079f93-d0d4-497c-8307-83a8a74e9419", "title": "PerformanceObserver()", "url": "/en-US/docs/Web/API/PerformanceObserver/PerformanceObserver", "tags": ["Constructor", "Reference", "PerformanceObserver", "API", "Web Performance"], "translations": [], "modified": "2016-08-11T15:14:09", "label": "PerformanceObserver()", "localization_tags": [], "locale": "en-US", "id": 168507, "last_edit": "2016-08-11T15:14:03", "summary": "The <strong><code>PerformanceObserver()</code></strong> constructor creates a new <a href=\"/en-US/docs/Web/API/PerformanceObserver\" title=\"The PerformanceObserver interface is used to observe performance measurement events and be notified of new performance entries as they are recorded in the browser's performance timeline.\"><code>PerformanceObserver</code></a> object with the given observer <code>callback</code>. The observer callback is invoked when <a href=\"/en-US/docs/Web/API/PerformanceEntry\" title=\"The PerformanceEntry object encapsulates a single performance metric that is part of the performance timeline. A performance entry can be directly created by making a performance mark or measure (for example by calling the mark() method) at an explicit point in an application. Performance entries are also created in indirect ways such as loading a resource (such as an image).\">performance entry events</a> are recorded for the <a href=\"/en-US/docs/Web/API/PerformanceEntry/entryType\" title=\"The entryType property returns the performance entry's type. The valid entryType values are:\">entry types</a> that have been registered, via the <a href=\"/en-US/docs/Web/API/PerformanceObserver/observe\" title=\"The observe() method of the PerformanceObserver interface is used to specify the set of performance interface types to observe. The performance observer's callback function will be invoked when a performance entry is recorded for one of the specified types.\"><code>observe()</code></a> method.", "sections": [{"id": "Quick_Links", "title": null}, {"id": "Syntax", "title": "Syntax"}, {"id": "Parameters", "title": "Parameters"}, {"id": "Example", "title": "Example"}, {"id": "Specifications", "title": "Specifications"}, {"id": "Browser_compatibility", "title": "Browser compatibility"}], "slug": "Web/API/PerformanceObserver/PerformanceObserver", "review_tags": []}