VRDisplayCapabilities.hasPosition

The hasPosition read-only property of the VRDisplayCapabilities interface returns a Boolean stating whether the VR display can track and return position information.

var hasItGotPosition = vrDisplayCapabilitiesInstance.hasPosition;

A Boolean.

function reportDisplays() {
  navigator.getVRDisplays().then(function(displays) {
    for(var i = 0; i < displays.length; i++) {
      var cap = displays[i].capabilities;
      // cap is a VRDisplayCapabilities object
      var listItem = document.createElement('li');
      listItem.innerHTML = '<strong>Display ' + (i+1) + '</strong>'
                   + '<br>VR Display ID: ' + displays[i].displayId
                   + '<br>VR Display Name: ' + displays[i].displayName
                   + '<br>Display can present content: ' + cap.canPresent
                   + '<br>Display is separate from the computer\'s main display: ' + cap.hasExternalDisplay
                   + '<br>Display can return position info: ' + cap.hasPosition
                   + '<br>Display can return orientation info: ' + cap.hasOrientation
                   + '<br>Display max layers: ' + cap.maxLayers;
      list.appendChild(listItem);
    }
  });
}

• WebVR API homepage.
• https://mixedreality.mozilla.org/ — demos, downloads, and other resources from the Mozilla VR team.