Javascript 如何仅从firebase中提取节点/值,而不提取键?
如何使用javascript仅从firebase提取节点而不提取密钥?换句话说,我只需要下面firebase中的键值对的值,这意味着我不需要下面的唯一键,只需要下面的键 目前,我的代码是Javascript 如何仅从firebase中提取节点/值,而不提取键?,javascript,dictionary,firebase,Javascript,Dictionary,Firebase,如何使用javascript仅从firebase提取节点而不提取密钥?换句话说,我只需要下面firebase中的键值对的值,这意味着我不需要下面的唯一键,只需要下面的键 目前,我的代码是 function PullFirebase() { new Firebase('https://myfirebase.firebaseIO.com/quakes').on('value', function (snapshot) { var S = snapshot.val();
function PullFirebase() {
new Firebase('https://myfirebase.firebaseIO.com/quakes').on('value', function (snapshot) {
var S = snapshot.val();
function printData(data) {
var f = eval(data);
console.log(data + "(" + f.length + ") = " + JSON.stringify(f).replace("[", "[\n\t").replace(/}\,/g, "},\n\t").replace("]", "\n]"));
}
printData(S);
});
}
PullFirebase();
这将在控制台中生成以下内容
[object Object](undefined) = {"-JStYZoJ7PWK1gM4n1M6":{"FID":"quake.2013p618454","agency":"WEL(GNS_Primary)","depth":"24.5703","latitude":"-41.5396","longitude":"174.1242","magnitude":"1.7345","magnitudetype":"M","origin_geom":"POINT (174.12425 -41.539614)","origintime":"2013-08-17T19:52:50.074","phases":"17","publicid":"2013p618454","status":"automatic","type":"","updatetime":"2013-08-17T19:54:11.27"},
"-JStYZsd6j4Cm6GZtrrD":{"FID":"quake.2013p618440","agency":"WEL(GNS_Primary)","depth":"26.3281","latitude":"-38.8725","longitude":"175.9561","magnitude":"2.6901","magnitudetype":"M","origin_geom":"POINT (175.95611 -38.872468)","origintime":"2013-08-17T19:45:25.076","phases":"13","publicid":"2013p618440","status":"automatic","type":"","updatetime":"2013-08-17T19:48:15.374"},...
但我只想要字典,比如
[{"FID":"quake.2013p618454","agency":"WEL(GNS_Primary)","depth":"24.5703","latitude":"-41.5396","longitude":"174.1242","magnitude":"1.7345","magnitudetype":"M","origin_geom":"POINT (174.12425 -41.539614)","origintime":"2013-08-17T19:52:50.074","phases":"17","publicid":"2013p618454","status":"automatic","type":"","updatetime":"2013-08-17T19:54:11.27"},{"FID":"quake.2013p597338","agency":"WEL(GNS_Primary)","depth":"5.0586","latitude":"-37.8523","longitude":"176.8801","magnitude":"2.2362","magnitudetype":"M","origin_geom":"POINT (176.88006 -37.852307)","origintime":"2013-08-10T00:21:54.989","phases":"17","publicid":"2013p597338","status":"automatic","type":"","updatetime":"2013-08-10T03:42:41.324"}...]
如果我理解正确,您希望将所有子对象置于
地震
下
这里通常有两种方法:
处理程序中,您可以使用以下方法跳过唯一ID:
forEach的forEach
函数是同步的,因此我们可以简单地等待循环完成,然后创建交叉过滤器
监视Firebase引用的子级
在这种情况下,最佳构造为:
var quakes = new Firebase('https://myfirebase.firebaseIO.com/quakes');
var quakeCount = 0;
quakes.on('child_added', function (snapshot) {
var quake = snapshot.val();
quakeCount++;
console.log("quakeCount="+quakeCount+", FID="+quake.FID);
});
quakes.on('child_removed', function (old_snapshot) {
var quake = old_snapshot.val();
quakeCount--;
console.log("quakeCount="+quakeCount+", removed FID="+quake.FID);
});
使用此代码结构,您可以主动监听添加和删除的地震。您仍然需要保留所有地震的数组,然后在child\u added
、child\u changed
和child\u removed
中对其进行修改
他们如何比较
当您第一次运行代码时,对子项的监视将产生与('value',
构造上的相同的数据。但是当以后在('value')上添加/删除子项时,
将再次接收所有地震,而打开('child_added',
和打开('child_removed',
将仅在有问题的地震中调用。如果我理解正确,您希望将所有子对象置于地震下
这里通常有两种方法:
获取父节点的值,并在子节点上循环
在将子节点添加/更新/删除到父节点时监视
您的方法与#1匹配,因此我将首先回答这个问题。我还将给出方法#2的示例,该方法在数据集更改时更有效
迭代Firebase引用的子级
在('value')上的处理程序中,您可以使用以下方法跳过唯一ID:
forEach的forEach
函数是同步的,因此我们可以简单地等待循环完成,然后创建交叉过滤器
监视Firebase引用的子级
在这种情况下,最佳构造为:
var quakes = new Firebase('https://myfirebase.firebaseIO.com/quakes');
var quakeCount = 0;
quakes.on('child_added', function (snapshot) {
var quake = snapshot.val();
quakeCount++;
console.log("quakeCount="+quakeCount+", FID="+quake.FID);
});
quakes.on('child_removed', function (old_snapshot) {
var quake = old_snapshot.val();
quakeCount--;
console.log("quakeCount="+quakeCount+", removed FID="+quake.FID);
});
使用此代码结构,您可以主动监听添加和删除的地震。您仍然需要保留所有地震的数组,然后在child\u added
、child\u changed
和child\u removed
中对其进行修改
他们如何比较
当您第一次运行代码时,对子项的监视将产生与('value',
构造上的相同的数据。但是当以后在('value')上添加/删除子项时,
将再次接收所有地震,而打开('child_added',
和打开(“child_removed”(已移除),
只会在有问题的地震中被调用