Checking for undefined prevents this code from failing with an error on older versions of web browsers. Returning a promise to allow you to determine success or failure of the operation was added more recently.
We check for this because in earlier versions of the HTML specification, play() didn't return a value. The first thing we do with the result of play() is make sure it's not undefined. getAutoplayPolicy (video ) = "allowed" ) If autoplay is only allowed for inaudible content, we mute the audio if autoplay is disallowed, we make sure that a placeholder image is displayed for the video. The code assumes video is an HTMLVideoElement media element using the tag or HTMLVideoElement, and that it is configured to autoplay with audio by default. The example below shows how you pass the mediaelement string to get the autoplay policy for all media elements in the document (pass audiocontext to get the policy for audio contexts). all media elements, or all audio contexts) in a document, or to check whether a specific media element or audio context can autoplay. The Navigator.getAutoplayPolicy() method can be used to check the autoplay policy for a type of media feature (i.e. Similarly, if you know that autoplay is not allowed at all, you might provide a default image for the video (using the poster attribute), or choose to defer loading the video until it is requested. If autoplay is important for your application, you may need to customize behavior based on whether or not autoplay is allowed, disallowed, or only supported for inaudible content.įor example, if your application needs to autoplay a video and you know that the page only allows the autoplay of inaudible content, you can either mute it or supply a video with no audio track. Example 2: Detecting whether autoplay is allowed
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