files/en-us/web/api/mediatracksupportedconstraints/channelcount/index.md
{{APIRef("Media Capture and Streams")}}
The {{domxref("MediaTrackSupportedConstraints")}} dictionary's
channelCount 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 channelCount 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 channelCount 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().channelCount;
result.textContent = supported ? "Supported!" : "Not supported!";
{{ EmbedLiveSample('Examples', 600, 80) }}
{{Specifications}}
{{Compat}}