在下面给出的代码中，我试图实现以下目标：
1.我有一个firestore数据库，其中有一个Orders集合，其中的数据字段（如时间）表示预期的交付时间，并使用值[“ Top Priority”，“ Mid Priority”，“ Low priority”]设置时间的时隙订单。
2.我试图创建一个字符串tfinal，该字符串根据优先级“最高优先级”>“中级优先级”>“低优先级”保存显示日期之前的订单。
3.然后在显示的当前日期添加订单，然后添加其他所有具有今天之后的预计交货日期的订单，这些订单由array signature = [“ <”，“ ==”，“>”];表示。
4.我尝试了异步等待，回调和承诺，但是我的逻辑失败了。
5，我的日期功能正确，Firestore配置也正确。
var temp, date2, col, pdes, t2, i, pri, signature, j, cl, tfinal, sig, pri2;
date2 = todaysdate(3); //todays date generates date like 26-10-2018 =>20181026 the date stored in fire store is also in this format
temp = tfinal = '';
i = j = 0;
cl = ["red", "blue", "green"]; //setting boundatey colours for html cards to be generated
pri = ["Top Priority", "Mid Priority", "Low priority"];
signature = ["<", "==", ">"];
function returnstring(callback) {
temp = "";
for (i = 0; i < signature.length; i++) { // used to iterate the signature/signs
for (j = 0; j < pri.length; j++) { //used to iterate priority
sig = signature[i];
pri2 = pri[j];
console.log(sig + ',' + pri2);
console.log(i + ',' + j);
tfinal += callback(sig, pri2); //callback function to make individual database query used async wait as well
console.log(tfinal); //output blank
}
}
$("#add1").append(tfinal);//jquery append html cards
}
returnstring(gettemp); //calling the above function
function gettemp(sig, pri2) { //callback function here
db.collection("Orders").where("date", sig, date2).where("timeslot", "==", pri2).onSnapshot(function(querySnapshot) {
console.log("one"); //function test check points
querySnapshot.forEach(function(doc) {
console.log("two"); //exicution not taking place from this log
console.log(doc.data()); //to log out availibility
pdes = doc.data().productlist;
t2 = "";
col = (signature[i] == "<") ? "red" : cl[j];
for (i = 0; i < pdes.length; i++) {
t2 = pdes[i].product + ' ' + pdes[i].
description + ' ' + pdes[i].quantity + ' ' +
pdes[i].unit
}
console.log(col + " " + t2);
temp += `<div class="card" style="margin:solid 3px ${col}">
<div class="card-header">${doc.data().date}</div>
<div class="card-body">${doc.data().name}<br>${t2}<br>Status:${doc.data().status}<br>${doc.data().placeofsupply}</div>
<div class="card-footer"><button type="button" class="btn btn-success"id="${doc.data().oid}">Success</button></div>
</div>`;
});
});
console.log(temp); //return coming out as blank
return temp;
}