Javascript 从firebase接收数据

我正在试验React和firebase。我有一个函数，当加载组件时，将读取数据库。连接正常，我收到了数据。但是，它们是对象，我想将它们结构化地放在一个数组中，稍后将读出。我只得到当前代码的错误： TypeError:无法读取属性“title”或未定义

有人知道我如何确保从Firebase收到的数据：

数据库：

使用此代码：

const newEvents = [];

useEffect(() => {
    let ref = Firebase.database().ref('/events');
    ref.on('value' , snapshot => {
        var state = snapshot.val();
        let arrayCount = loopStateEvents(state);
        console.log(state);

        for(var i = 0; i < arrayCount; i++){

            newEvents.push({title: state[i].title, id: state[i].id, resourceId: state[i].resourceId,start: new Date(state[i].yearStart,state[i].monthStart,state[i].dayStart,state[i].hourStart,state[i].minuteStart,state[i].secondStart),end: new Date(state[i].yearStart,state[i].monthStart,state[i].dayStart,state[i].hourEnd,state[i].minuteEnd,state[i].secondEnd)});
            //setEventDb([...eventDb,{title: state[i].title, id: state[i].id, resourceId: state[i].resourceId,start: new Date(state[i].yearStart,state[i].monthStart,state[i].dayStart,state[i].hourStart,state[i].minuteStart,state[i].secondStart),end: new Date(state[i].yearStart,state[i].monthStart,state[i].dayStart,state[i].hourEnd,state[i].minuteEnd,state[i].secondEnd)}]);
        }


    });
},[] );

const loopStateEvents = function(object){
   var length = 0;
  for( var key in object ) {
      if( object.hasOwnProperty(key) ) {
          ++length;
      }
  }
  return length;
}

请执行以下操作：

let ref = Firebase.database().ref('/events');
    ref.on('value' , snapshot => {
        snapshot.forEach((childSnap) => {
        let state = childSnap.val());
        console.log(childSnap);
            newEvents.push({title: state.title, id: state.id, resourceId: state.resourceId,start: new Date(state.yearStart,state.monthStart,state.dayStart,state.hourStart,state.minuteStart,state.secondStart),end: new Date(state.yearStart,state.monthStart,state.dayStart,state.hourEnd,state.minuteEnd,state.secondEnd)});          
    });

使用

forEach

在数组内迭代，然后使用

childSnap

使用点表示法访问属性

useEffect(() => {
    let ref = Firebase.database().ref('/events');
    ref.on('value' , snapshot => {
        var state = snapshot.val();
        let events = []
        for (var key in state) {
          events.push(state[key]);
        }
    });
},[] );

使用

for（var key in state）

可以直接使用从firebase返回的对象并推入事件数组，而不需要对象的长度。 您可以通过以下方式添加自定义属性：

state[key].start = new Date(state[key].yearStart,state[key].monthStart,state[key].dayStart,state[key].hourStart,state[key].minuteStart,state[key].secondStart)

state[key].start = new Date(state[key].yearStart,state[key].monthStart,state[key].dayStart,state[key].hourStart,state[key].minuteStart,state[key].secondStart)