files/en-us/web/api/mediatracksupportedconstraints/facingmode/index.md
{{APIRef("Media Capture and Streams")}}
The {{domxref("MediaTrackSupportedConstraints")}} dictionary's
facingMode property is a read-only Boolean value which is
present (and set to true) in the object returned by
{{domxref("MediaDevices.getSupportedConstraints()")}} if and only if the
{{Glossary("user agent")}} supports the facingMode constraint. If the
constraint isn't supported, it's not included in the list, so this value will never be
false.
You can access the supported constraints dictionary by calling
navigator.mediaDevices.getSupportedConstraints().
This property is present in the dictionary (and its value is always true)
if the user agent supports the facingMode constraint. If the property isn't
present, this property is missing from the supported constraints dictionary, and you'll
get {{jsxref("undefined")}} if you try to look at its value.
<div id="result"></div>
#result {
font:
14px "Arial",
sans-serif;
}
const result = document.getElementById("result");
const supported = navigator.mediaDevices.getSupportedConstraints().facingMode;
result.textContent = supported ? "Supported!" : "Not supported!";
{{ EmbedLiveSample('Examples', 600, 80) }}
{{Specifications}}
{{Compat}}