Table of Contents

Class PerformanceNavigationTiming

Namespace
CSharpToJavaScript.APIs.JS
Assembly
CSharpToJavaScript.dll

The PerformanceNavigationTiming interface provides methods and properties to store and retrieve metrics regarding the browser's document navigation events. For example, this interface can be used to determine how much time it takes to load or unload a document.

[Value("PerformanceNavigationTiming")]
public class PerformanceNavigationTiming : PerformanceResourceTiming
Inheritance
PerformanceNavigationTiming
Inherited Members

Remarks

Only the current document is included in the performance timeline, so there is only one PerformanceNavigationTiming object in the performance timeline. It inherits all of the properties and methods of PerformanceResourceTiming and PerformanceEntry.

The following diagram shows all of the timestamp properties defined in PerformanceNavigationTiming.

Timestamp diagram listing timestamps in the order in which they are recorded for the fetching of a document

-Navigation
-PerformanceNavigation

See also on MDN

Constructors

PerformanceNavigationTiming() 

public PerformanceNavigationTiming()

Properties

ActivationStart

CAUTION
Non-standard
The activationStart read-only property represents the time between when a document starts prerendering and when it is activated. 
[Value("activationStart")]
public Number ActivationStart { get; }

Property Value

Number

A Number representing the duration between document prerendering start and activation in milliseconds.The value is 0 if the page has not prerendered or is still prerendering.

Remarks

-Speculation Rules API
-Speculative loading

See also on MDN

CriticalCHRestart

NOTE
Experimental
A website can indicate that a particular Client Hint is critical to the page by including it in a Critical-CH HTTP response header (as well as the Accept-CH HTTP request header which is needed for all client hints whether critical or not). Doing so will trigger a connection restart if the hint listed in the Critical-CH HTTP response header could have been, but wasn't, included in the HTTP request initially sent. If the browser does not support that client hint, it is ignored and no connection restart occurs. 
[Value("criticalCHRestart")]
public Number CriticalCHRestart { get; }

Property Value

Number

A Number representing the number of milliseconds elapsed since StartTime when the connection restart occurred in milliseconds.If the value is 0 the connection was not restarted.

Remarks

The criticalCHRestart read-only property represents the time at which the connection restart occurred.

-Client hints
-User-Agent Client Hints API
-Improving user privacy and developer experience with User-Agent Client Hints (developer.chrome.com)
-Accept-CH
-Critical-CH

See also on MDN

DomComplete

The domComplete read-only property returns a Number representing the time immediately before the user agent sets the document's readyState to "complete".

[Value("domComplete")]
public Number DomComplete { get; }

Property Value

Number

A Number representing the time immediately before the user agent sets the document's readyState to "complete".

Remarks

See also the complete state of ReadyState which corresponds to this property and refers to the state in which the document and all sub-resources have finished loading. The state also indicates that the Windowload event is about to fire.

-ReadyState

See also on MDN

DomContentLoadedEventEnd

The domContentLoadedEventEnd read-only property returns a Number representing the time immediately after the current document's DOMContentLoaded event handler completes.

[Value("domContentLoadedEventEnd")]
public Number DomContentLoadedEventEnd { get; }

Property Value

Number

A Number representing the time immediately after the current document's DOMContentLoaded event handler completes.

Remarks

Typically frameworks and libraries wait for the DOMContentLoaded event before starting to run their code. We can use the domContentLoadedEventEnd and the domContentLoadedEventStart properties to calculate how long this takes to run.

-DOMContentLoaded

See also on MDN

DomContentLoadedEventStart

The domContentLoadedEventStart read-only property returns a Number representing the time immediately before the current document's DOMContentLoaded event handler starts.

[Value("domContentLoadedEventStart")]
public Number DomContentLoadedEventStart { get; }

Property Value

Number

A Number representing the time immediately before the current document's DOMContentLoaded event handler starts.

Remarks

Typically frameworks and libraries wait for the DOMContentLoaded event before starting to run their code. We can use the domContentLoadedEventStart and the domContentLoadedEventEnd properties to calculate how long this takes to run.

-DOMContentLoaded

See also on MDN

DomInteractive

The domInteractive read-only property returns a Number representing the time immediately before the user agent sets the document's readyState to "interactive".

[Value("domInteractive")]
public Number DomInteractive { get; }

Property Value

Number

A Number representing the time immediately before the user agent sets the document's readyState to "interactive".

Remarks

NOTE

This property is not Time to interactive (TTI). This property refers to the time when DOM construction is finished and interaction to it from JavaScript is possible. See also the interactive state of ReadyState which corresponds to this property.

Measuring DOM processing time may not be consequential unless your site has a very large HTML source to a construct a Document Object Model from.

If there is no parser-blocking JavaScript then the DOMContentLoaded event (see domContentLoadedEventStart for the timestamp) will fire immediately after domInteractive.

-ReadyState

See also on MDN

LoadEventEnd

The loadEventEnd read-only property returns a Number representing the time immediately after the current document's load event handler completes.

[Value("loadEventEnd")]
public Number LoadEventEnd { get; }

Property Value

Number

A Number representing the time immediately after the current document's load event handler completes.

Remarks

-load event

See also on MDN

LoadEventStart

The loadEventStart read-only property returns a Number representing the time immediately before the current document's load event handler starts.

[Value("loadEventStart")]
public Number LoadEventStart { get; }

Property Value

Number

A Number representing the time immediately before the current document's load event handler starts.

Remarks

-load event

See also on MDN

NotRestoredReasons

NOTE
Experimental
The notRestoredReasons read-only property of the PerformanceNavigationTiming interface returns a NotRestoredReasons object providing report data on reasons why the current document was blocked from using the back/forward cache ({{Glossary("bfcache")}}) on navigation. 
[Value("notRestoredReasons")]
public NotRestoredReasons? NotRestoredReasons { get; }

Property Value

NotRestoredReasons

When the associated PerformanceNavigationTiming object represents a history navigation, notRestoredReasons returns a NotRestoredReasons object.When the PerformanceNavigationTiming object does not represent a history navigation, notRestoredReasons will return null. This is useful for determining whether bfcache is not relevant to a particular navigation (as opposed to notRestoredReasons not being supported, in which case it would return undefined).

NOTE
notRestoredReasons may return null despite the navigation type being reported as a back/forward navigation. These circumstances include duplicating a back/forward navigation in a new tab and restoring a back/forward navigation tab after a browser restart. In such cases, some browsers copy the navigation type from the original tab, but as these are not actually back/forward navigations, notRestoredReasons returns null.

Remarks

-Monitoring bfcache blocking reasons
-PerformanceResourceTiming

See also on MDN

RedirectCount

The redirectCount read-only property returns a number representing the number of redirects since the last non-redirect navigation in the current browsing context.

[Value("redirectCount")]
public ushort RedirectCount { get; }

Property Value

ushort

The redirectCount property can have the following values:

Remarks

The higher the number of redirects on a page, the longer the page load time. To improve the performance of your web page, avoid multiple redirects.

The RedirectStart and RedirectEnd properties can be used to measure redirection time. Note that they will return 0 for cross-origin redirects.

Note that client side redirects, such as <meta http-equiv="refresh" content="0; url=https://example.com/"> are not considered here.

-RedirectStart
-RedirectEnd

See also on MDN

Type

The type read-only property returns the type of navigation.

[Value("type")]
public NavigationTimingType Type { get; }

Property Value

NavigationTimingType

The type property can have the following values:

Remarks

You can use this property to categorize your navigation timing data as each of these types will have different performance characteristics. Users going back and forth might experience a faster site than users performing navigation for the first time or submitting forms, etc.

For example, if your site provides new content frequently, you might want to refresh that content using Fetch or similar and avoid users having to hit reload for the entire page all the time. The "reload" type can help you find pages that are reloaded frequently.

See also on MDN

UnloadEventEnd

The unloadEventEnd read-only property returns a Number representing the time immediately after the previous document's unload event handler completes.

[Value("unloadEventEnd")]
public Number UnloadEventEnd { get; }

Property Value

Number

The unloadEventEnd property can have the following values:

Remarks

-unload event

See also on MDN

UnloadEventStart

The unloadEventStart read-only property returns a Number representing the time immediately before the previous document's unload event handler starts.

[Value("unloadEventStart")]
public Number UnloadEventStart { get; }

Property Value

Number

The unloadEventStart property can have the following values:

Remarks

-unload event

See also on MDN

Methods

ToJSON()

The toJSON() method of the PerformanceNavigationTiming interface is a {{Glossary("Serialization","serializer")}}; it returns a JSON representation of the PerformanceNavigationTiming object.

[Value("toJSON")]
public Object ToJSON()

Returns

Object

A {{jsxref("JSON")}} object that is the serialization of the PerformanceNavigationTiming object.

Remarks

-JSON

See also on MDN

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