当前位置：文江博客知识库 en-US 文档 Web API PerformanceEntry

PerformanceEntry - Web APIs 编辑

The PerformanceEntry object encapsulates a single performance metric that is part of the performance timeline. A performance entry can be directly created by making a performance mark or measure (for example by calling the mark() method) at an explicit point in an application. Performance entries are also created in indirect ways such as loading a resource (such as an image).

PerformanceEntry instances will always be one of the following subtypes:

Note:

This feature is available in Web Workers.

Properties

PerformanceEntry.name Read only: A value that further specifies the value returned by the PerformanceEntry.entryType property. The value of both depends on the subtype. See property page for valid values.
PerformanceEntry.entryType Read only: A DOMString representing the type of performance metric such as, for example, "mark". See property page for valid values.
PerformanceEntry.startTime Read only: A DOMHighResTimeStamp representing the starting time for the performance metric.
PerformanceEntry.duration Read only: A DOMHighResTimeStamp representing the time value of the duration of the performance event.

Methods

PerformanceEntry.toJSON(): Returns a JSON representation of the PerformanceEntry object.

Example

The following example checks all PerformanceEntry properties to see if the browser supports them and if so, write their values to the console.

function print_PerformanceEntries() {
  // Use getEntries() to get a list of all performance entries
  var p = performance.getEntries();
  for (var i=0; i < p.length; i++) {
    console.log("PerformanceEntry[" + i + "]");
    print_PerformanceEntry(p[i]);
  }
}
function print_PerformanceEntry(perfEntry) {
  var properties = ["name",
                    "entryType",
                    "startTime",
                    "duration"];

  for (var i=0; i < properties.length; i++) {
    // Check each property
    var supported = properties[i] in perfEntry;
    if (supported) {
      var value = perfEntry[properties[i]];
      console.log("... " + properties[i] + " = " + value);
    } else {
      console.log("... " + properties[i] + " is NOT supported");
    }
  }
}

Specifications

Specification	Status	Comment
Resource Timing Level 3	Editor's Draft
Resource Timing Level 2	Working Draft
Resource Timing Level 1	Candidate Recommendation	Adds the `PerformanceResourceTiming` interface and the `resource` value for `entryType`.
Navigation Timing Level 2	Working Draft
Navigation Timing	Recommendation	Adds the `PerformanceNavigationTiming` interface and the `navigation` value for `entryType`.
User Timing Level 2	Working Draft
User Timing	Recommendation	Adds the `PerformanceMark` and `PerformanceMeasure` interfaces as well as the `mark` and `measure` values for `entryType`.
Frame Timing	Draft	Adds the `PerformanceFrameTiming` interface and the `frame` value for `entryType`.
Performance Timeline Level 2 The definition of 'PerformanceEntry' in that specification.	Candidate Recommendation	Added `toJSON()` serializer method.
Performance Timeline The definition of 'PerformanceEntry' in that specification.	Recommendation	Initial definition.