Fire an event when number of face more than two

Question

This is my code of face detection with a JavaScript API. I want to add a condition when I detect more than two faces, then do something. I want to create an extension on Chrome Browser, but I don't how can I add this condition in my code

const video = document.getElementById("video");
let predictedAges = [];

Promise.all([
  faceapi.nets.tinyFaceDetector.loadFromUri("/models"),
  faceapi.nets.faceLandmark68Net.loadFromUri("/models"),
  faceapi.nets.faceRecognitionNet.loadFromUri("/models"),
  faceapi.nets.faceExpressionNet.loadFromUri("/models"),
  faceapi.nets.ageGenderNet.loadFromUri("/models")
]).then(startVideo);

function startVideo() {
  navigator.getUserMedia(
    { video: {} },
    stream => (video.srcObject = stream),
    err => console.error(err)
  );
}

video.addEventListener("playing", () => {
  const canvas = faceapi.createCanvasFromMedia(video);
  document.body.append(canvas);

  const displaySize = { width: video.width, height: video.height };
  faceapi.matchDimensions(canvas, displaySize);

  setInterval(async () => {
    const detections = await faceapi
      .detectAllFaces(video, new faceapi.TinyFaceDetectorOptions())
      .withFaceLandmarks()
      .withFaceExpressions()
      .withAgeAndGender();
    const resizedDetections = faceapi.resizeResults(detections, displaySize);

    canvas.getContext("2d").clearRect(0, 0, canvas.width, canvas.height);

    faceapi.draw.drawDetections(canvas, resizedDetections);
    faceapi.draw.drawFaceLandmarks(canvas, resizedDetections);
    faceapi.draw.drawFaceExpressions(canvas, resizedDetections);

    const age = resizedDetections[0].age;
    const interpolatedAge = interpolateAgePredictions(age);
    const bottomRight = {
      x: resizedDetections[0].detection.box.bottomRight.x - 50,
      y: resizedDetections[0].detection.box.bottomRight.y
    };

    new faceapi.draw.DrawTextField(
      [`${faceapi.utils.round(interpolatedAge, 0)} years`],
      bottomRight
    ).draw(canvas);
  }, 100);
});

function interpolateAgePredictions(age) {
  predictedAges = [age].concat(predictedAges).slice(0, 30);
  const avgPredictedAge =
    predictedAges.reduce((total, a) => total + a) / predictedAges.length;
  return avgPredictedAge;
}

Answer 1

to answer the question i finaly found the solution by using the propreties of detections object

to get the number of face detected in the recognization i'm using

detections.length

so problem resolved !!

if(detections.length>=2) do something !!