read-only property returns an
unsigned long long representing the moment,
in milliseconds since the UNIX epoch, when the browser sent the request to obtain the
actual document, from the server or from a cache. If the transport layer fails after the
start of the request and the connection is reopened, this property will be set to the
time corresponding to the new request.
time = performanceTiming.requestStart;
The definition of 'PerformanceTiming.requestStart' in that specification.
BCD tables only load in the browser
PerformanceTiminginterface it belongs to.