The getSupportedConstraints() method of the MediaDevices interface returns an object based on the MediaTrackSupportedConstraints dictionary, whose member fields each specify one of the constrainable properties the user agent understands.

None.

A new object based on the MediaTrackSupportedConstraints dictionary listing the constraints supported by the user agent. Because only constraints supported by the user agent are included in the list, each of these Boolean properties has the value true.

This example outputs a list of the constraints supported by your browser.

const constraintList = document.querySelector("#constraintList");
const supportedConstraints = navigator.mediaDevices.getSupportedConstraints();

for (const constraint of Object.keys(supportedConstraints)) {
  const elem = document.createElement("li");
  elem.innerHTML = `<code>${constraint}</code>`;
  constraintList.appendChild(elem);
}