Promise.all与Firebase DataSnapshot.forEach [英] Promise.all with Firebase DataSnapshot.forEach
本文介绍了Promise.all与Firebase DataSnapshot.forEach的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有两个HTML选择（下拉列表），它们是从名为states的Firebase节点填充的（请参阅下图）。选择一个城市后，下面的功能会触发，并应该检索在该城市发生的所有会议。有一个单独的会议节点，每个会议有各种键/值对，如街道，时间等。
我想（我想）使用Promise 。因为我想在DataSnapshot.forEach中执行一次Firebase读取（每个会议ID上的一个.once）。下面是不行的。
函数loadMeetings（city，state）{
// $（'＃meetingsTable'） .empty（）;
var reads = [];
ref.child（'states'）。child（state）.child（city）.once（'value'）。then（function（snapshot）{
snapshot.forEach（function（childSnapshot）{
var id = childSnapshot.key（）;
var dfd = ref.child（'meetings'）。child（id）.once（'value'）。then（function（snap）{
// Promise已完成
}，function（error）{
// Promise was rejected。
console.error（error）;
}）;
reads.push（dfd）;
}）;
}，函数（error）{
// Promise被拒绝。
console.error（error）;
}）;
Promise.all（reads）.then（function（values）{
console.log（values）; // [snap，snap，snap]
}）;
$ b
{geofire：{25dbab9c-8e4e-45ce-a69b-8641b6579560：{.priority：9q5cc9ye4w，g：9q5cc9ye4w，l：[34.0677809，-118.4016105] }，3d2c7948-16e5-466c-b0d8-0a9e24ed7529：{.priority：7zzzzzzzzz，g：7zzzzzzzzz，l：[0,0]}，3fc846d4-7e55-4134- ：dhyy1zhnu1，g：dhyy1zhnu1，l：[27.8130538，-80.42524100000003]}，5952bd9f-8438-44b0-addb-a5b806dab5da：{a0f5-9393aaf02269 9vw1zzv421，g：9vw1zzv421，l：[31.288082，-92.46505450000001]}，7001c8a7-c4f0-44ba-a4fc-2dba32097cc6：{.priority：9vqe68qs06， g：9vqe68qs06，l：[30.1046126，-91.99056969999998]}，ecb350d - 优先级：9vrk9tstc9，g：9vrk9tstc9，l：[30.353474，-90.98251599999998]}}，标记：{addMeeting ：< form class = \outline \>< div class = \row \>< h1 class = \blue topTitle col-xs-10 col-xs-offset -1 col-md-4 col-md-offset-4 \>新会议< / h1>< / div>< br>< div class = \form-group row \> ;< div class = \col-xs-10 col-xs-offset-1 col-md-3 col-md-offset-2 \> < input type = \text \class = \form-control \id = \meetingName\placeholder = \Meeting Name \> < / div>< div class = \col-xs-10 col-xs-offset-1 col-md-4 col-md-pull-1 \> < input type = \text \class = \form-control \id = \meetingStreet\placeholder = \Street\required> < / div>< div class = \form-group row \>< div class = \col-xs-10 col-xs-offset-1 col-md -3 col-md-offset-2 \> < input type = \text \class = \form-control \id = \meetingCity\placeholder = \City \required> < / div>< div class = \col-xs-10 col-xs-offset-1 col-md-2 col-md-pull-1 \> < select class = \form-control c-select \id = \meetingState\required>< option> Alabama< / option>< option>阿拉斯加< / option>< option> ;亚利桑那< /选项><选项>阿肯色< /选项><选项>加州< /选项><选项>科罗拉多< /选项><选项>康涅狄格< /选项><选项>特拉华< /选项> ;<选项>佛罗里达< /选项><选项>佐治亚< /选项><选项>夏威夷< /选项><选项>爱达荷州< /选项><选项>伊利诺斯< /选项><选项>印第安纳< /选项><选项>衣阿华< /选项><选项>堪萨斯< /选项><选项>肯塔基< /选项><选项>路易斯安那< /选项><选项>缅因< /选项> <选项>马里兰< /选项><选项>马萨诸塞< /选项><选项>密歇根< /选项><选项>明尼苏达< /选项><选项>密西西比< /选项><选项> Missour新泽西州< / option>< option>蒙大拿州< / option>< option>内布拉斯加州< / option>< option>内华达州< / option>< option> New Hampshire< / option><选项>< option>新墨西哥< / option>< option>纽约< / option>< option>北卡罗来纳< / option>< option>北达科他< / option>< option>俄亥俄< / option> < / option>< option>< / option>< option>俄勒冈< / option>< option>宾夕法尼亚< / option>< option> Rhode Island< / option>< option> South Carolina< / option>< < / option>< / option> Vermont< / option>< option> Virginia< / option>< /选项>< option>华盛顿< / option><选项>西弗吉尼亚< / option><选项>威斯康星< / option>< option>怀俄明< / option>< / select>< / div> < div class = \col-xs-10 col-xs-offset-1 col-md-2 col-md-pull-2 \> < input type = \text \class = \form-control \id = \meetingZip\placeholder = \ZIP \required> < / div>< div class = \form-group row \>< div class = \col-xs-5 col-xs-offset-1 col-md -2 col-md-offset-2 \> < input type = \text \class = \form-control \id = \latitude \placeholder = \latitude \disabled> < / div>< div class = \col-xs-5 col-md-2 pull-left \> < input type = \text \class = \form-control \id = \longitude \placeholder = \longitude \disabled> < / div>< div class = \form-group row \>< div class = \col-xs-10 col-xs-offset-1 col-md -2 col-md-offset-2 \>< select class = \form-control c-select \id = \weekday \>< option>星期天< / option> ;<选项>周一< /选项><选项>周二< /选项><选项>周三< /选项><选项>周四< /选项><选项>周五< /选项><选项> < / div>< / div>< / class>< >< div class = \form-inline \>< div class = \form-group \>< select class = \form-control c-select \ < / option>< option> 1< / option>< option> 2< / option>< option> 3< / option>< option>选项→5< /选项><选项→6< /选项><选项大于7< /选项><选项> 8 LT; /选项><选项> 9< / option>< option> 10< / option>< option> 11< / option>< option> 12< / option>< / select>< select class = < / option>：00< / option>< option>：15< / option>< option>：30< / option>< option> ;< / option>< / select>< select class = \form-control c-select \id = \timeframe \>< option> AM< / option><< ;选项>下一个< /选项>< / select>< / div>< / div>< / div>< / div>< div class = \form-group row \> < div class = \col-xs-10 col-xs-offset-1 col-md-4 col-md-offset-2 \> < label class = \\radio-inline c-input c-radio \> < input type = \radio \name = \meetingType \id = \openMeeting \> < span class = \c-indicator \>< / span>打开会议< / label> < label class = \\radio-inline c-input c-radio \> < input type = \radio \name = \meetingType \id = \closedMeeting \checked> < span class = \c-indicator \>< / span>关闭会议< / label> < / div>< div class = \form-group row \>< div class = \col-xs-5 col-xs-offset-1 col-md -2 col-md-offset-2 \> < label class = \c-input c-checkbox \> < input type = \checkbox \id = \mensOnly \> < span class = \c-indicator \>< / span> < / label>< br>< label class = \c-input c-checkbox \> < input type = \checkbox \id = \womensOnly \> < span class = \c-indicator \>< / span>女装专用< / label>< br>< label class = \c-input c-checkbox \> < input type = \checkbox\id = \childcare \> < span class = \c-indicator \>< / span>育儿< / label> < / div>< div class = \col-xs-5 col-xs-offset-1 col-md-2 col-md-pull-1 \> < label class = \c-input c-checkbox \> < input type = \checkbox \id = \meditation \> < span class = \c-indicator \>< / span>冥想< / label>< br>< label class = \c-input c-checkbox \> < input type = \checkbox \id = \speaker \> < span class = \c-indicator \>< / span>扬声器< / label>< br>< label class = \c-input c-checkbox \> < input type = \checkbox \id = \step \> < span class = \c-indicator \>< / span>步骤< / label> < / div>< div class = \form-group row \>< div class = \col-xs-5 col-xs-offset-1 col-md -2 col-md-offset-2 \> < label class = \c-input c-checkbox \> < input type = \checkbox \id = \spanish \> < span class = \c-indicator \>< / span> Español< / label>< br>< label class = \c-input c-checkbox \> < input type = \checkbox \id = \bigBook \> < span class = \c-indicator \>< / span> Big Book< / label>< br>< label class = \c-input c-checkbox \> < input type = \checkbox \id = \discussion \> < span class = \c-indicator \>< / span>讨论< / label> < / div>< div class = \col-xs-5 col-xs-offset-1 col-md-2 col-md-pull-1 \> < label class = \c-input c-checkbox \> < input type = \checkbox \id = \tradition \> < span class = \c-indicator \>< / span>传统< / label>< br>< label class = \c-input c-checkbox \> < input type = \checkbox \id = \beginner \> < span class = \c-indicator \>< / span>初学者< / label> < / div>< div class = \form-group row \>< div class = \col-xs-5 col-xs-offset-8 col-md -2 col-md-offset-8 \> < input class = \btn btn-primary \type = \submit\id = \submit\>< / input> < / div>< / div>< / form>，admin：< ul id = \tabs \class = \nav nav-tabs \> < li class = \nav-item \> < a data-toggle = \tab \class = \nav-link active \href = \＃adminWelcome\role = \tab\> Welcome&一个> < / li>< li class = \nav-item dropdown \>数据切换= \下拉式菜单\href = \＃\角色= \按钮\aria-haspopup = \true \aria-expanded = \false \>会议< / a> < div class = \dropdown-menu \> < a data-toggle = \tab \class = \dropdown-item \href = \＃addMeeting \> Add< / a> < a data-toggle = \tab \class = \dropdown-item \href = \＃manageMeeting \>管理< / a> < / div>< / li>< li class = \nav-item dropdown \>数据切换= \下拉式菜单\href = \＃\角色= \按钮\aria-haspopup = \true \aria-expanded = \false \>使用者< / a> < div class = \dropdown-menu \> < a data-toggle = \tab \class = \dropdown-item \href = \＃addUser \> Add< / a> < a data-toggle = \tab \class = \dropdown-item \href = \＃manageUser \>管理< / a> < / DIV>< /立GT;< / UL> < div class = \tab-content \> < div id = \adminWelcome \class = \tab-pane fade in active \role = \tabpanel \> < h3 class = \topTitle \>欢迎。< / h3>< div class = \loader \>< img src = \images / loading.gif\ >< p class = \blue\>运行脚本...< / p>< / div>< script> adminInit（）;< / script> < / div>< div id = \addMeeting \class = \tab-pane fade \role = \tabpanel \>< div class = \loader \\ >< img src = \ images images / loading.gif\>< p class = \blue \>运行脚本...< / p>< / div> ;< / div>< div id = \manageMeeting \class = \tab-pane fade \role = \tabpanel \>< div class = \loader \>< img src = \images / loading.gif\>< p class = \blue\>正在运行脚本...< / p>< / div>< / div>< div id = \addUser\class = \tab-pane fade\role = \tabpanel \>< div class = \ loader \>< img src = \images / loading.gif\>< p class = \blue \>运行脚本...< / p>< / div>< / div>< div id = \manageUser\class = \tab-pane fade \role = \tabpanel \>< div class = \ loader \>< img src = \images / load >< p class = \blue\> Running Scripts ...< / p>< / div>< / div>< / div> admin \\欢迎：< p>这是管理员欢迎窗格< / p>，login：< div class = \row topMargin myLogin col-xs-10 col-xs-offset- md-6 col-md-offset-3 \>< br>< h1 class = \\>登入< / h1>< br>< div class = \ btn-group-vertical \role = \group \>< button class = \btn btn-secondary myButton \id = \facebook\>< img src = \images / facebook.png\class = \middle \alt = \Facebook logo \height = \24 \> Facebook< / button>< button class = \btn btn-secondary myButton \id = \google\>< img src = \images / google.png\class = \middle \alt = \Google logo \height = \24 \> Google< / button>< button class = \btn btn-secondary myButton \id = \twitter\>< img src = \images / twitter.png\class = \middle \alt = \Twitter logo \height = \24 \> < / div>< / div>< br>< br>< / div>，manageMeeting：< form class = \form-inline outline \> ;< div class = \form-group \>< label for = \ddState \>过滤器& nbsp; < / div>< / class>< / div>< div class = \form- group \>< label for = \ddState \>& nbsp;& nbsp;& nbsp; < / label>< / class>< / form>< / div>< / form>}，会议：{25dbab9c-8e4e-45ce-a69b-8641b6579560：{作者：罗恩·罗伊斯顿，初学者：true，bigBook：真，托儿：假，城市天，星期天，讨论：假，小时：4，键：25dbab9c-8e4e-45ce-a69b-8641b6579560，纬度：34.0677809， ：，经度：-118.4016105，冥想：false，meetingOpen：false，min：：00，name：highrise，onlyMen：false，onlyWomen真正的西班牙语：真，说话人：假，国家：加州，步：假，街道：111 rodeo，时间范围：下午，时间戳：1457470568863 ，传统：true，type：，user：脸谱：196986260658947，zip：90210}，3d2c 7948-16e5-466c-b0d8-0a9e24ed7529：{作者：罗恩·罗伊斯顿，初学者：假，大书：假，育儿：假，城市：接力胭脂 ：星期日讨论：假，小时：1，键：3d2c7948-16e5-466c-b0d8-0a9e24ed7529，纬度：0，层：，经度：0，冥想：假，会议开始：假，分钟：：00，名称：asdf，只有男人：假，仅女人：假，西班牙语假，说话人：假，状态：路易斯安那，步：假，街：234 kjhkj，时间范围：上午，时间戳：1457470215505，传统 ，type：，user：Facebook：196986260658947，zip：70817}，3fc846d4-7e55-4134-a0f5-9393aaf02269：{author：Ron Royston初学者：假，bigBook：真，保育：真，城市：迈阿密，日：星期日， 讨论：真，小时：1，键：3fc846d4-7e55-4134-a0f5-9393aaf02269，纬度：27.8130538，层：，经度：-80.42524100000003， 冥想：false，meetingOpen：假，min：00，name：beach，onlyMen：false，onlyWomen：false，西班牙语 ：假，州：佛罗里达，步：假，街：120 a1a，时间范围：上午，时间戳：1457470499310，传统：假，类型 ，user：facebook：196986260658947，zip：33101}，5952bd9f-8438-44b0-addb-a5b806dab5da：{author：Ron Royston，beginner bigBook：假，托儿：假，城市：亚历山大，日：星期日，讨论：假，小时：1，钥匙：5952bd9f-8438 -44b0-addb-a5b806dab5da，纬度：31.288082，层：，经度：-92.465 05450000001冥想：false，meetingOpen：false，min：：00，name：howdy，onlyMen：false，onlyWomen：false，spanish：false，扬声器：假，国家：路易斯安那，步：假，街：5676城市公园，时间范围：上午，时间戳：1457470284850，传统键入：，user：Facebook：196986260658947，zip：71301}，7001c8a7-c4f0-44ba-a4fc-2dba32097cc6：{author：Ron Royston，beginner ：假，bigBook：假，托儿：假，城市：lafayette，天：星期日，讨论：假，小时：1 7001c8a7-c4f0-44ba-a4fc-2dba32097cc6，latitude：30.1046126，layer：，longitude：-91.99056969999998，meditation：false，meetingOpen：false，min：：00 ，name：test3，onlyMen：false，onlyWomen：false， 西班牙语：假，发言人：假，国家：路易斯安那，步：假，街：234 kjhkj，时间范围：上午，时间戳：1457470252872，传统：false，type：，user：Facebook：196986260658947，zip：70500}，ecb350d6-6664-4f95-9c1c-2fd1d2f11a40：{author：Ron罗伊斯顿，初学者：假，大书：假，保育：假，城市：接力胭脂，日：星期日，讨论：假，小时：5 ，key：ecb350d6-6664-4f95-9c1c-2fd1d2f11a40，latitude：30.353474，layer：，longitude：-90.98251599999998，meditation：true，meetingOpen min：：00，name：test1，onlyMen：false，onlyWomen：false，西班牙语：假，扬声器：真，状态：louisiana步：假，街：18432湖虹膜，时间框架：下午，蒂姆estamp：1457470192281，tradition：false，type：，user：Facebook：196986260658947，zip：70817}}，states：{california：{los angeles：{25dbab9c-8e4e-45ce-a69b-8641b6579560：true}}，florida：{miami：{3fc846d4-7e55-4134-a0f5-9393aaf02269：true}}，louisiana： {alexandria：{5952bd9f-8438-44b0-addb-a5b806dab5da：true}，baton rouge：{3d2c7948-16e5-466c-b0d8-0a9e24ed7529：true，ecb350d6-6664-4f95-9c1c- 2fd1d2f11a40：true}，lafayette：{7001c8a7-c4f0-44ba-a4fc-2dba32097cc6：true}}}}
解决方案 <你必须执行 Promise.all ，然后在内填充数组，然后回调：
function loadMeetings（city，state）{
// $（'＃meetingsTable'）。empty（）;
return ref.child（'states'）。child（state）.child（city）.once（'value'）。then（function（snapshot）{
var reads = [];
// ^^^^^^^^^^^^^^
snapshot.forEach（function（childSnapshot）{
var id = childSnapshot.key（）;
var promise （函数（snap）{
// Promise被实现。
}，函数（错误）= ref.child（'meetings'）。child（id）.once {
// Promise was rejected。
console.error（error）;
}）;
reads.push（promise）;
}）;
return Promise.all（reads）;
// ^^^^^^^^^^^^^^^^^
}，function（error）{
//
console.error（error）;
））。then（function（values）{
console.log（values）; // [snap，snap，snap]
}）; b
$，如果快照是一个数组，你可以通过使用 map 而不是 forEach 来简化你的代码。I have a couple of HTML select's (dropdowns) that are populated from a Firebase node called "states" (see image below). Upon choosing a city, the below function fires and should retrieve all meetings occurring in that City. There is a separate "meetings" node and each meeting has various key/value pairs such as street, time, etc.
I (think that I) want to use Promise.all because I want to do a Firebase read (a .once on each meetingID) inside the DataSnapshot.forEach. Below does not work.
function loadMeetings(city,state){
//$('#meetingsTable').empty();
var reads = [];
ref.child('states').child(state).child(city).once('value').then(function(snapshot) {
snapshot.forEach(function(childSnapshot) {
var id = childSnapshot.key();
var dfd = ref.child('meetings').child(id).once('value').then(function(snap) {
// The Promise was fulfilled.
}, function(error) {
// The Promise was rejected.
console.error(error);
});
reads.push( dfd );
});
}, function(error) {
// The Promise was rejected.
console.error(error);
});
Promise.all(reads).then(function(values) {
console.log(values); // [snap, snap, snap]
});
}
{
"geofire" : {
"25dbab9c-8e4e-45ce-a69b-8641b6579560" : {
".priority" : "9q5cc9ye4w",
"g" : "9q5cc9ye4w",
"l" : [ 34.0677809, -118.4016105 ]
},
"3d2c7948-16e5-466c-b0d8-0a9e24ed7529" : {
".priority" : "7zzzzzzzzz",
"g" : "7zzzzzzzzz",
"l" : [ 0, 0 ]
},
"3fc846d4-7e55-4134-a0f5-9393aaf02269" : {
".priority" : "dhyy1zhnu1",
"g" : "dhyy1zhnu1",
"l" : [ 27.8130538, -80.42524100000003 ]
},
"5952bd9f-8438-44b0-addb-a5b806dab5da" : {
".priority" : "9vw1zzv421",
"g" : "9vw1zzv421",
"l" : [ 31.288082, -92.46505450000001 ]
},
"7001c8a7-c4f0-44ba-a4fc-2dba32097cc6" : {
".priority" : "9vqe68qs06",
"g" : "9vqe68qs06",
"l" : [ 30.1046126, -91.99056969999998 ]
},
"ecb350d6-6664-4f95-9c1c-2fd1d2f11a40" : {
".priority" : "9vrk9tstc9",
"g" : "9vrk9tstc9",
"l" : [ 30.353474, -90.98251599999998 ]
}
},
"markup" : {
"addMeeting" : "<form class=\"outline\"><div class=\"row\"><h1 class=\"blue topTitle col-xs-10 col-xs-offset-1 col-md-4 col-md-offset-4\">New Meeting</h1></div><br><div class=\"form-group row\"><div class=\"col-xs-10 col-xs-offset-1 col-md-3 col-md-offset-2\"> <input type=\"text\" class=\"form-control\" id=\"meetingName\" placeholder=\"Meeting Name\"> </div><div class=\"col-xs-10 col-xs-offset-1 col-md-4 col-md-pull-1\"> <input type=\"text\" class=\"form-control\" id=\"meetingStreet\" placeholder=\"Street\" required> </div></div><div class=\"form-group row\"><div class=\"col-xs-10 col-xs-offset-1 col-md-3 col-md-offset-2\"> <input type=\"text\" class=\"form-control\" id=\"meetingCity\" placeholder=\"City\" required> </div><div class=\"col-xs-10 col-xs-offset-1 col-md-2 col-md-pull-1\"> <select class=\"form-control c-select\" id=\"meetingState\" required><option>Alabama </option><option>Alaska</option><option>Arizona</option><option>Arkansas</option><option>California</option><option>Colorado</option><option>Connecticut</option><option>Delaware</option><option>Florida</option><option>Georgia</option><option>Hawaii</option><option>Idaho</option><option>Illinois</option><option>Indiana</option><option>Iowa</option><option>Kansas</option><option>Kentucky</option><option>Louisiana</option><option>Maine</option><option>Maryland</option><option>Massachusetts</option><option>Michigan</option><option>Minnesota</option><option>Mississippi</option><option>Missouri</option><option>Montana</option><option>Nebraska</option><option>Nevada</option><option>New Hampshire</option><option>New Jersey</option><option>New Mexico</option><option>New York</option><option>North Carolina</option><option>North Dakota</option><option>Ohio</option><option>Oklahoma</option><option>Oregon</option><option>Pennsylvania</option><option>Rhode Island</option><option>South Carolina</option><option>South Dakota</option><option>Tennessee</option><option>Texas</option><option>Utah</option><option>Vermont</option><option>Virginia</option><option>Washington</option><option>West Virginia</option><option>Wisconsin</option><option>Wyoming</option></select></div><div class=\"col-xs-10 col-xs-offset-1 col-md-2 col-md-pull-2\"> <input type=\"text\" class=\"form-control\" id=\"meetingZip\" placeholder=\"ZIP\" required> </div></div><div class=\"form-group row\"><div class=\"col-xs-5 col-xs-offset-1 col-md-2 col-md-offset-2\"> <input type=\"text\" class=\"form-control\" id=\"latitude\" placeholder=\"latitude\" disabled> </div><div class=\"col-xs-5 col-md-2 pull-left\"> <input type=\"text\" class=\"form-control\" id=\"longitude\" placeholder=\"longitude\" disabled> </div></div><div class=\"form-group row\"><div class=\"col-xs-10 col-xs-offset-1 col-md-2 col-md-offset-2\"><select class=\"form-control c-select\" id=\"weekday\"><option>Sunday</option><option>Monday</option><option>Tuesday</option><option>Wednesday</option><option>Thursday</option><option>Friday</option><option>Saturday</option></select></div><div class=\"col-xs-10 col-xs-offset-1 col-md-3 col-md-pull-1\"><div class=\"form-inline\"><div class=\"form-group\"><select class=\"form-control c-select\" id=\"hour\"><option>1</option><option>2</option><option>3</option><option>4</option><option>5</option><option>6</option><option>7</option><option>8</option><option>9</option><option>10</option><option>11</option><option>12</option></select><select class=\"form-control c-select\" id=\"minute\"><option>:00</option><option>:15</option><option>:30</option><option>:45</option></select><select class=\"form-control c-select\" id=\"timeframe\"><option>AM</option><option>PM</option></select></div></div></div></div><div class=\"form-group row\"><div class=\"col-xs-10 col-xs-offset-1 col-md-4 col-md-offset-2\"> <label class=\"radio-inline c-input c-radio\"> <input type=\"radio\" name=\"meetingType\" id=\"openMeeting\"> <span class=\"c-indicator\"></span> Open Meeting </label> <label class=\"radio-inline c-input c-radio\"> <input type=\"radio\" name=\"meetingType\" id=\"closedMeeting\" checked> <span class=\"c-indicator\"></span> Closed Meeting </label> </div></div><div class=\"form-group row\"><div class=\"col-xs-5 col-xs-offset-1 col-md-2 col-md-offset-2\"> <label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"mensOnly\"> <span class=\"c-indicator\"></span> Mens Only </label><br><label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"womensOnly\"> <span class=\"c-indicator\"></span> Womens Only </label><br><label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"childcare\"> <span class=\"c-indicator\"></span> Childcare </label> </div><div class=\"col-xs-5 col-xs-offset-1 col-md-2 col-md-pull-1\"> <label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"meditation\"> <span class=\"c-indicator\"></span> Meditation </label><br><label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"speaker\"> <span class=\"c-indicator\"></span> Speaker </label><br><label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"step\"> <span class=\"c-indicator\"></span> Step </label> </div></div><div class=\"form-group row\"><div class=\"col-xs-5 col-xs-offset-1 col-md-2 col-md-offset-2\"> <label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"spanish\"> <span class=\"c-indicator\"></span> Español </label><br><label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"bigBook\"> <span class=\"c-indicator\"></span> Big Book </label><br><label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"discussion\"> <span class=\"c-indicator\"></span> Discussion </label> </div><div class=\"col-xs-5 col-xs-offset-1 col-md-2 col-md-pull-1\"> <label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"tradition\"> <span class=\"c-indicator\"></span> Tradition </label><br><label class=\"c-input c-checkbox\"> <input type=\"checkbox\" id=\"beginner\"> <span class=\"c-indicator\"></span> Beginner </label> </div></div><div class=\"form-group row\"><div class=\"col-xs-5 col-xs-offset-8 col-md-2 col-md-offset-8\"> <input class=\"btn btn-primary\" type=\"submit\" id=\"submit\"></input> </div></div></form>",
"admin" : "<ul id=\"tabs\" class=\"nav nav-tabs\"> <li class=\"nav-item\"> <a data-toggle=\"tab\" class=\"nav-link active\" href=\"#adminWelcome\" role=\"tab\">Welcome</a> </li><li class=\"nav-item dropdown\"> <a class=\"nav-link dropdown-toggle\" data-toggle=\"dropdown\" href=\"#\" role=\"button\" aria-haspopup=\"true\" aria-expanded=\"false\">Meetings</a> <div class=\"dropdown-menu\"> <a data-toggle=\"tab\" class=\"dropdown-item\" href=\"#addMeeting\">Add</a> <a data-toggle=\"tab\" class=\"dropdown-item\" href=\"#manageMeeting\">Manage</a> </div></li><li class=\"nav-item dropdown\"> <a class=\"nav-link dropdown-toggle\" data-toggle=\"dropdown\" href=\"#\" role=\"button\" aria-haspopup=\"true\" aria-expanded=\"false\">Users</a> <div class=\"dropdown-menu\"> <a data-toggle=\"tab\" class=\"dropdown-item\" href=\"#addUser\">Add</a> <a data-toggle=\"tab\" class=\"dropdown-item\" href=\"#manageUser\">Manage</a> </div></li></ul> <div class=\"tab-content\"> <div id=\"adminWelcome\" class=\"tab-pane fade in active\" role=\"tabpanel\"> <h3 class=\"topTitle\">Welcome.</h3><div class=\"loader\"><img src=\"images/loading.gif\"><p class=\"blue\">Running Scripts...</p></div><script>adminInit();</script> </div><div id=\"addMeeting\" class=\"tab-pane fade\" role=\"tabpanel\"><div class=\"loader\"><img src=\"images/loading.gif\"><p class=\"blue\">Running Scripts...</p></div></div><div id=\"manageMeeting\" class=\"tab-pane fade\" role=\"tabpanel\"><div class=\"loader\"><img src=\"images/loading.gif\"><p class=\"blue\">Running Scripts...</p></div></div><div id=\"addUser\" class=\"tab-pane fade\" role=\"tabpanel\"><div class=\"loader\"><img src=\"images/loading.gif\"><p class=\"blue\">Running Scripts...</p></div></div><div id=\"manageUser\" class=\"tab-pane fade\" role=\"tabpanel\"><div class=\"loader\"><img src=\"images/loading.gif\"><p class=\"blue\">Running Scripts...</p></div></div></div>",
"adminWelcome" : "<p>This is the admin welcome pane</p>",
"login" : "<div class=\"row topMargin myLogin col-xs-10 col-xs-offset-1 col-md-6 col-md-offset-3\"><br><h1 class=\"\">Log In</h1><br><div class=\"btn-group-vertical\" role=\"group\"><button class=\"btn btn-secondary myButton\" id=\"facebook\"><img src=\"images/facebook.png\" class=\"middle\" alt=\"Facebook logo\" height=\"24\"> Facebook</button><button class=\"btn btn-secondary myButton\" id=\"google\"><img src=\"images/google.png\" class=\"middle\" alt=\"Google logo\" height=\"24\"> Google</button><button class=\"btn btn-secondary myButton\" id=\"twitter\"><img src=\"images/twitter.png\" class=\"middle\" alt=\"Twitter logo\" height=\"24\"> Twitter</button></div><br><br><br></div>",
"manageMeeting" : "<form class=\"form-inline outline\"><div class=\"form-group\"><label for=\"ddState\">Filter </label><select class=\"form-control\" id=\"ddState\" disabled></select></div><div class=\"form-group\"><label for=\"ddState\"> </label><select class=\"form-control state\" id=\"ddCity\" disabled></select></div></form>"
},
"meetings" : {
"25dbab9c-8e4e-45ce-a69b-8641b6579560" : {
"author" : "Ron Royston",
"beginner" : true,
"bigBook" : true,
"childcare" : false,
"city" : "los angeles",
"day" : "sunday",
"discussion" : false,
"hour" : "4",
"key" : "25dbab9c-8e4e-45ce-a69b-8641b6579560",
"latitude" : 34.0677809,
"layer" : "",
"longitude" : -118.4016105,
"meditation" : false,
"meetingOpen" : false,
"min" : ":00",
"name" : "highrise",
"onlyMen" : false,
"onlyWomen" : true,
"spanish" : true,
"speaker" : false,
"state" : "california",
"step" : false,
"street" : "111 rodeo",
"timeframe" : "pm",
"timestamp" : 1457470568863,
"tradition" : true,
"type" : "",
"user" : "facebook:196986260658947",
"zip" : "90210"
},
"3d2c7948-16e5-466c-b0d8-0a9e24ed7529" : {
"author" : "Ron Royston",
"beginner" : false,
"bigBook" : false,
"childcare" : false,
"city" : "baton rouge",
"day" : "sunday",
"discussion" : false,
"hour" : "1",
"key" : "3d2c7948-16e5-466c-b0d8-0a9e24ed7529",
"latitude" : 0,
"layer" : "",
"longitude" : 0,
"meditation" : false,
"meetingOpen" : false,
"min" : ":00",
"name" : "asdf",
"onlyMen" : false,
"onlyWomen" : false,
"spanish" : false,
"speaker" : false,
"state" : "louisiana",
"step" : false,
"street" : "234 kjhkj",
"timeframe" : "am",
"timestamp" : 1457470215505,
"tradition" : false,
"type" : "",
"user" : "facebook:196986260658947",
"zip" : "70817"
},
"3fc846d4-7e55-4134-a0f5-9393aaf02269" : {
"author" : "Ron Royston",
"beginner" : false,
"bigBook" : true,
"childcare" : true,
"city" : "miami",
"day" : "sunday",
"discussion" : true,
"hour" : "1",
"key" : "3fc846d4-7e55-4134-a0f5-9393aaf02269",
"latitude" : 27.8130538,
"layer" : "",
"longitude" : -80.42524100000003,
"meditation" : false,
"meetingOpen" : false,
"min" : ":00",
"name" : "beach",
"onlyMen" : false,
"onlyWomen" : false,
"spanish" : true,
"speaker" : false,
"state" : "florida",
"step" : false,
"street" : "120 a1a",
"timeframe" : "am",
"timestamp" : 1457470499310,
"tradition" : false,
"type" : "",
"user" : "facebook:196986260658947",
"zip" : "33101"
},
"5952bd9f-8438-44b0-addb-a5b806dab5da" : {
"author" : "Ron Royston",
"beginner" : true,
"bigBook" : false,
"childcare" : false,
"city" : "alexandria",
"day" : "sunday",
"discussion" : false,
"hour" : "1",
"key" : "5952bd9f-8438-44b0-addb-a5b806dab5da",
"latitude" : 31.288082,
"layer" : "",
"longitude" : -92.46505450000001,
"meditation" : false,
"meetingOpen" : false,
"min" : ":00",
"name" : "howdy",
"onlyMen" : false,
"onlyWomen" : false,
"spanish" : false,
"speaker" : false,
"state" : "louisiana",
"step" : false,
"street" : "5676 city park",
"timeframe" : "am",
"timestamp" : 1457470284850,
"tradition" : true,
"type" : "",
"user" : "facebook:196986260658947",
"zip" : "71301"
},
"7001c8a7-c4f0-44ba-a4fc-2dba32097cc6" : {
"author" : "Ron Royston",
"beginner" : false,
"bigBook" : false,
"childcare" : false,
"city" : "lafayette",
"day" : "sunday",
"discussion" : false,
"hour" : "1",
"key" : "7001c8a7-c4f0-44ba-a4fc-2dba32097cc6",
"latitude" : 30.1046126,
"layer" : "",
"longitude" : -91.99056969999998,
"meditation" : false,
"meetingOpen" : false,
"min" : ":00",
"name" : "test3",
"onlyMen" : false,
"onlyWomen" : false,
"spanish" : false,
"speaker" : false,
"state" : "louisiana",
"step" : false,
"street" : "234 kjhkj",
"timeframe" : "am",
"timestamp" : 1457470252872,
"tradition" : false,
"type" : "",
"user" : "facebook:196986260658947",
"zip" : "70500"
},
"ecb350d6-6664-4f95-9c1c-2fd1d2f11a40" : {
"author" : "Ron Royston",
"beginner" : false,
"bigBook" : false,
"childcare" : false,
"city" : "baton rouge",
"day" : "sunday",
"discussion" : false,
"hour" : "5",
"key" : "ecb350d6-6664-4f95-9c1c-2fd1d2f11a40",
"latitude" : 30.353474,
"layer" : "",
"longitude" : -90.98251599999998,
"meditation" : true,
"meetingOpen" : false,
"min" : ":00",
"name" : "test1",
"onlyMen" : false,
"onlyWomen" : false,
"spanish" : false,
"speaker" : true,
"state" : "louisiana",
"step" : false,
"street" : "18432 lake iris",
"timeframe" : "pm",
"timestamp" : 1457470192281,
"tradition" : false,
"type" : "",
"user" : "facebook:196986260658947",
"zip" : "70817"
}
},
"states" : {
"california " : {
"los angeles" : {
"25dbab9c-8e4e-45ce-a69b-8641b6579560" : true
}
},
"florida " : {
"miami" : {
"3fc846d4-7e55-4134-a0f5-9393aaf02269" : true
}
},
"louisiana " : {
"alexandria" : {
"5952bd9f-8438-44b0-addb-a5b806dab5da" : true
},
"baton rouge" : {
"3d2c7948-16e5-466c-b0d8-0a9e24ed7529" : true,
"ecb350d6-6664-4f95-9c1c-2fd1d2f11a40" : true
},
"lafayette" : {
"7001c8a7-c4f0-44ba-a4fc-2dba32097cc6" : true
}
}
}
}
解决方案 You have to execute the Promise.all after you filled the array with promises, i.e. inside the then callback:
function loadMeetings(city,state) {
//$('#meetingsTable').empty();
return ref.child('states').child(state).child(city).once('value').then(function(snapshot) {
var reads = [];
// ^^^^^^^^^^^^^^
snapshot.forEach(function(childSnapshot) {
var id = childSnapshot.key();
var promise = ref.child('meetings').child(id).once('value').then(function(snap) {
// The Promise was fulfilled.
}, function(error) {
// The Promise was rejected.
console.error(error);
});
reads.push(promise);
});
return Promise.all(reads);
// ^^^^^^^^^^^^^^^^^
}, function(error) {
// The Promise was rejected.
console.error(error);
}).then(function(values) {
console.log(values); // [snap, snap, snap]
});
}
Btw, if snapshot is an array you can simplify your code by using map instead of forEach.
这篇关于Promise.all与Firebase DataSnapshot.forEach的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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