The domainLookupStart property must return the time immediately before the user agent starts the domain name lookup for the current document. If a persistent connection is used or the current document is retrieved from relevant application caches or local resources, this attribute must return the same value as fetchStart.
An Integer value that represents the time immediately before the user agent starts the domain name lookup for the current document.
- Navigation Timing, Section 4.2
If a page is retrieved from an application cache, domainLookupStart has the same value as fetchStart.
The value reported by the domainLookupStart property represents the number of milliseconds between the recorded time and midnight January 1, 1970 (UTC).
Windows Internet Explorer 9. This property is supported only for documents displayed in IE9 Standards mode. For more information, see Defining Document Compatibility.
The following example shows how to calculate the amount of time to complete a domain name request for the document.
var oTiming = window.performance.timing; var iTimeMS = oTiming.domainLookupEnd - oTiming.domainLookupStart;