RTCPeerConnection.getStats() - Web APIs 编辑

The RTCPeerConnection method getStats() returns a promise which resolves with data providing statistics about either the overall connection or about the specified MediaStreamTrack.

Syntax

promise = rtcPeerConnection.getStats(selector)

Parameters

selector Optional

A MediaStreamTrack for which to gather statistics. If this is null (the default value), statistics will be gathered for the entire RTCPeerConnection.

Return value

A Promise which resolves with an RTCStatsReport object providing connection statistics. The contents of the report depend on the selector as well as other details of the connection.

Exceptions

This method does not throw exceptions; instead, it rejects the returned promise with one of the following errors:

InvalidAccessError

There is no RTCRtpSender or RTCRtpReceiver whose track matches the specified selector, or selector matches more than one sender or receiver.

Obsolete syntax

Previously, getStats() used success and failure callbacks to report the results to you, instead of using a promise. 

This version of getStats() is obsolete; in addition, the data it returns is entirely different from the current specification, and the form of that data was never documented. This form of getStats() has been or will soon be removed from most browsers; you should not use it, and should update existing code to use the new promise-based version. Check the Browser compatibility table to verify the state of this method.

promise = rtcPeerConnection.getStats(selector, successCallback, failureCallback) 

Parameters

selector Optional

A MediaStreamTrack for which to gather statistics. If this is null (the default value), statistics will be gathered for the entire RTCPeerConnection.

successCallback

A callback function to call when the stats have been retrieved. The function receives as input a single parameter: an RTCStatsReport with the collected statistics. No output is expected from the function.

failureCallback

A function to call when an error occurs while attempting to collect statistics. The callback receives as input the exception (a DOMException object describing the error which occurred. No return value is expected from the callback.

Example

This example creates a periodic function using setInterval() that collects statistics for an RTCPeerConnection every second, generating an HTML-formatted report and inserting it into a specific element in the DOM.

window.setInterval(function() {
  myPeerConnection.getStats(null).then(stats => {
    let statsOutput = "";

    stats.forEach(report => {
      statsOutput += `<h2>Report: ${report.type}</h3>\n<strong>ID:</strong> ${report.id}<br>\n` +
                     `<strong>Timestamp:</strong> ${report.timestamp}<br>\n`;

      // Now the statistics for this report; we intentially drop the ones we
      // sorted to the top above

      Object.keys(report).forEach(statName => {
        if (statName !== "id" && statName !== "timestamp" && statName !== "type") {
          statsOutput += `<strong>${statName}:</strong> ${report[statName]}<br>\n`;
        }
      });
    });

    document.querySelector(".stats-box").innerHTML = statsOutput;
  });
}, 1000);

This works by calling getStats(), then, when the promise is resolved, iterates over the RTCStats objects on the returned RTCStatsReport. A section is created for each report with a header and all of the statistics below, with the type, ID, and timestamp handled specially to place them at the top of the list.

Once the HTML for the report is generated, it is injected into the element whose class is "stats-box" by setting its innerHTML property.

Specifications

Browser compatibility

BCD tables only load in the browser