Camera-flip.js

switchCamera() {
  this.props.switchCamera() // yup, we literally just call it on the <App />
}

// hey, let's also let users double-tap to flip the camera around
let prevDate = Date.now(); // set this up once
evalDoubleTap() {
  const newDate = Date.now(); // 
  if(newDate < prevDate + 200) { // if 2 taps happen within 200ms of each other, it's a double tap
    this.switchCamera();
  }
  prevDate = newDate;
}