如何使用javaScript在Firebase数据库中检索嵌套的子值? [英] How to retrieve nested child value in Firebase database using javaScript?

问题描述

这是我的Fireabse数据库结构.我想检索不是硬编码值的20170116键的数据.它是动态键.我有一些键和值，如:

Here is my Fireabse database structure. I want to retrieve data of 20170116 keys that is not a hard coded value. It's dynamic keys. I got some keys and values like :

这是我的功能:

function getData(prospectId) {
    database.ref('users/'+prospectId).once('value').then(function(snapshot) {
        var prospectId = snapshot.key ;
        console.log("prospectId : "+ prospectId); // output is : prospectId : 1104812

        snapshot.forEach(function(childSnapshot) {
            var businessUrl = childSnapshot.key;
            console.log("businessUrl : "+ businessUrl); // output is : businessUrl : http:\\www.abc.com
            var dates = Object.keys(childSnapshot.val());
            console.log("dates : "+ dates); //output is : dates : 20170116,20170117,20170119,20170121
            var singleDate = dates[0];
            console.log("singleDate : "+ singleDate); //output is : singleDate : 20170116
        });
    });
}  

getData(1104812);

那么如何获取20170116日期数据或快照?

So how to get 20170116 date data or snapshot ?

推荐答案

您正在将值侦听器附加到/users/1104812.因此，您在回调中获取的快照将包含位于以下子节点:20170116，20170117和20170119.

You're attaching a value listener to /users/1104812. So the snapshot you get in your callback will contain the child nodes under that: 20170116, 20170117 and 20170119.

当您遍历子级(使用snapshot.forEach(function()时，您的childSnapshot将依次成为每个节点.

When you loop over the children (with snapshot.forEach(function() your childSnapshot will become each of those nodes in turn.

这些节点都没有子节点clientUrl或districtId，这些子节点在树中更深一层:

None of these nodes has a child clientUrl or districtId, those are one level deeper into the tree:

database.ref('users/'+prospectId).once('value').then(function(snapshot) {
  var prospectId = snapshot.key ;

  snapshot.forEach(function(snapshot1) {
    console.log(snapshot1.key); // e.g. "http://..."
    snapshot.forEach(function(snapshot2) {
      console.log(childSnapshot.key); // e.g. "20170116"
      childSnapshot.forEach(function(snapshot3) {
        console.log(grandchildSnapshot.key); // e.g. "-Kb9...gkE"
        console.log(grandchildSnapshot.val().districtId); // "pne"
      });
    });
  });
});

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