如何返回异步回调的值？

Question

这是我的代码，如果数据库中存在一个元素，这是对mysql的查询，返回1或0。我想知道我如何获得价值？

if (typeof requestPostAnimationFrame !== 'function') {
  monkeyPatchRequestPostAnimationFrame();
}

requestAnimationFrame( animationFrameCallback );
requestPostAnimationFrame( postAnimationFrameCallback );

// monkey-patches requestPostAnimationFrame
//!\ Can not be called from inside a requestAnimationFrame callback
function monkeyPatchRequestPostAnimationFrame() {
  console.warn('using a MessageEvent workaround');
  const channel = new MessageChannel();
  const callbacks = [];
  let timestamp = 0;
  let called = false;
  channel.port2.onmessage = e => {
    called = false;
    const toCall = callbacks.slice();
    callbacks.length = 0;
    toCall.forEach(fn => {
      try {
        fn(timestamp);
      } catch (e) {}
    });
  }
  window.requestPostAnimationFrame = function(callback) {
    if (typeof callback !== 'function') {
      throw new TypeError('Argument 1 is not callable');
    }
    callbacks.push(callback);
    if (!called) {
      requestAnimationFrame((time) => {
        timestamp = time;
        channel.port1.postMessage('');
      });
      called = true;
    }
  };
}


// void loops, look at your dev-tools' timeline to see where each fires
function animationFrameCallback() {
  requestAnimationFrame( animationFrameCallback );
}
function postAnimationFrameCallback() {
  requestPostAnimationFrame( postAnimationFrameCallback )
}