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First of all, I have to say that the react native is a third party library. Questions about react native is not supported on Microsoft Q&A.
What I could do is just talk from the UWP side, there are native UWP APIs could for speech recognition- Windows.Media.SpeechRecognition Namespace
SpeechRecognition API could help to detect what the user is saying and also detect voice command. For more information, you might need to check Speech recognition
In the end, if you have questions about react native, you could ask in the official forum of the react native.
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