ap.onAppResume(CALLBACK)

<script src="https://gw.alipayobjects.com/as/g/h5-lib/alipayjsapi/3.1.1/alipayjsapi.inc.min.js"></script>

<h2 class="am-ft-center">点击 Home 键回到手机桌面</h2>
<script>
  var output = document.querySelector('#J_output');
  var time;
  ap.onAppPause(function(){
    time = Date.now();
  });
  ap.onAppResume(function(){
    time = Date.now() - time;
    ap.alert('应用在后台运行' + time/1000 + 's');
  });
</script>