TheMediaTrackSupportedConstraints dictionary'sframeRate property is a read-only Boolean value which ispresent (and set totrue) in the object returned byMediaDevices.getSupportedConstraints() if and only if theuser agent supports theframeRate constraint.

If the constraint isn't supported, it's not included in the list, so this value will never befalse.

TheframeRate constraint can be used to establish acceptable upper and lower bounds on the video frame rate for a new video track, or to specify an exact frame rate that must be provided for the request to succeed.Checking the value of this property lets you determine if the user agent allows constraining the video track configuration by frame rate. See theexample to see how this can be used.

Value

This property is present in the dictionary if the user agent supports theframeRate constraint.If the property isn't present, the user agent doesn't allow specifying limits on the frame rate for video tracks.

Examples

This simple example looks to see if your browser supports constraining the frame rate when requesting video tracks.

JavaScript

const result = document.getElementById("result");const supported = navigator.mediaDevices.getSupportedConstraints().frameRate;result.textContent = supported ? "Supported!" : "Not supported!";

HTML

<div></div>

CSS

#result {  font:    14px "Arial",    sans-serif;}

Result

The output, showing if your browser supports theframeRate constraint, is:

While this example is trivial, you can replace the simple output of "Supported" vs."Not supported" with code to provide alternative methods for presenting the audiovisual information you want to share with the user or otherwise work with.

Specifications

Browser compatibility

See also

• Media Capture and Streams API
• MediaDevices.getSupportedConstraints()
• MediaTrackSupportedConstraints
• MediaStreamTrack