{"json_modified": "2016-03-28T08:49:04.883292", "uuid": "fd7ac0f4-50f2-4cef-88a0-07aed76e4a29", "title": "PerformanceNavigationTiming.unloadEventStart", "url": "/en-US/docs/Web/API/PerformanceNavigationTiming/unloadEventStart", "tags": ["Web Performance", "Reference", "API", "Property"], "translations": [], "modified": "2016-03-02T12:18:23", "label": "PerformanceNavigationTiming.unloadEventStart", "localization_tags": [], "locale": "en-US", "id": 171591, "last_edit": "2016-03-02T12:18:20", "summary": "The <strong><code>unloadEventStart</code></strong> property returns a <a href=\"/en-US/docs/Web/API/DOMHighResTimeStamp\" title=\"The DOMHighResTimeStamp type is a double and is used to store a time value. The value could be a discrete point in time or the difference in time between two discrete points in time. The unit is milliseconds and should be accurate to 5 &#xB5;s (microseconds). However, if the browser is unable to provide a time value accurate to 5 microseconds (because, for example, due to hardware or software constraints), the browser can represent the value as a time in milliseconds accurate to a millisecond.\"><code>timestamp</code></a> representing the time value equal to the time immediately before the user agent starts the unload event of the previous document. If there is no previous document, this property returns <code>0</code>.", "sections": [{"id": "Quick_Links", "title": null}, {"id": "Syntax", "title": "Syntax"}, {"id": "Return_Value", "title": "Return Value"}, {"id": "Example", "title": "Example"}, {"id": "Specifications", "title": "Specifications"}, {"id": "Browser_compatibility", "title": "Browser compatibility"}], "slug": "Web/API/PerformanceNavigationTiming/unloadEventStart", "review_tags": ["technical"]}