Navigation timing makes it easy to measure the real-world speed and performance of websites and locate problem areas that need tuning.
For example, navigation timing can help you locate latency problems by helping you precisely monitor customer webpage navigation and track the timing of user activities.
performance.timing is generated based on all requests and responses (but not including the ajax ones).
console.log(window.performance);
Will show you the timing object:
connectEnd // Time when server connection is finished.
connectStart // Time just before server connection begins.
domComplete // Time just before document readiness completes.
domContentLoadedEventEnd // Time after DOMContentLoaded event completes.
domContentLoadedEventStart // Time just before DOMContentLoaded starts.
domInteractive // Time just before readiness set to interactive.
domLoading // Time just before readiness set to loading.
domainLookupEnd // Time after domain name lookup.
domainLookupStart // Time just before domain name lookup.
fetchStart // Time when the resource starts being fetched.
loadEventEnd // Time when the load event is complete.
loadEventStart // Time just before the load event is fired.
navigationStart // Time after the previous document begins unload.
redirectCount // Number of redirects since the last non-redirect.
redirectEnd // Time after last redirect response ends.
redirectStart // Time of fetch that initiated a redirect.
requestStart // Time just before a server request.
responseEnd // Time after the end of a response or connection.
responseStart // Time just before the start of a response.
timing // Reference to a performance timing object.
navigation // Reference to performance navigation object.
performance // Reference to performance object for a window.
type // Type of the last non-redirect navigation event.
unloadEventEnd // Time after the previous document is unloaded.
unloadEventStart // Time just before the unload event is fired.