Return a value from function inside promise - node.js

Question

I am trying to return the array shiftInfo from the function csData() within a promise.
function crewsense(){
var request = CS.find({});
request
.then(result => {
var created = result[0].created,
currentTime = moment(),
diff = (currentTime - created);
if(diff < 84600000){
console.log("Current Token is Valid");
var access_token = result[0].access_token;
console.log('Obtaining Crewsense Shift Data');
return access_token
}else{
console.log("Current Token is invalid. Updating Token");
csToken();
}
}).then(access_token => {
csData(access_token) //I am trying to get this function to return async data.
}).then(shiftInfo => { //I want to use the data here.
})
Here is the csData function:
function csData(csKey) {
const dayURL = {
method: 'get',
url: 'https://api.crewsense.com/v1/schedule?start='+today+'%2007:30:00&end='+tomorrow+'%2007:30:00',
headers:{
Authorization: csKey,
}
}
const request = axios(dayURL)
request
.then(result => {
var shiftInfo = [];
var thisShift = [];
var onDuty = result.data.days[moment().format("YYYY-MM-DD")].assignments;
thisShift.push(result.data.days[moment().format("YYYY-MM-DD")].day_color);
var persons = [];
var i = 0;
for(var i=0; i<onDuty.length; i++){
let station = onDuty[i].name
for(var x=0; x<onDuty[i].shifts.length; x++){
var person = {
name: onDuty[i].shifts[x].user.name,
position: onDuty[i].shifts[x].qualifiers[0].name,
station: station
}
persons.push(person);
}
}
shiftInfo = [{thisShift}, {persons}];
// console.log(shiftInfo)
return shiftInfo
})
.catch(error => console.error('csData error:', error))
}
I have attempted assigning var shiftInfo = csData(access_token) w/o success and several other ways to call the csData function. I have attempted reading other like problems on here and I have just ended up confused. If someone can point me in the right direction or please point out the fix I might be able to get it to click in my head.
I appreciate everyone's time.
Thanks!

Answer 1

Whatever you return inside a then, will be passed to the next then callback. If you return a Promise, the result of the promise will be sent to the next then callback:
new Promise((resolve) => {
// We resolve to the value we want
resolve("yay");
}).then((value) => {
// In the first then, value will be "yay"
console.log("First then:", value);
// Then we return a new value "yay x2"
return value + " x2";
}).then((value) => {
// In this second then, we received "yay x2"
console.log("Second then:", value);
// Then we return a promise that will resolve to "yay x2 again"
return new Promise((resolve) => {
setTimeout(() => {
resolve(value + " again");
}, 1000);
});
}).then((value) => {
// After a second (when the returned Promise is resolved) we get the new value "yay x2 again"
console.log("Third then:", value);
// And now we return a Promise that will reject
return new Promise((resolve, reject) => {
setTimeout(() => {
reject(new Error("wtf"));
}, 1000);
});
}).catch((error) => {
// This catch on the whole promise chain will catch any promise rejected
console.log(error.toString());
});
So simply csData must return the promise is creating, and you need to return that promise to the then callback you want:
[...]
}).then(access_token => {
return csData(access_token) //I am trying to get this function to return async data.
}).then(shiftInfo => { //I want to use the data here.
console.log(shiftInfo);
}).catch((err) => {
// Whatever...
});
function csData(csKey) {
[...]
return request.then(result => {
[...]
}
Because you are returning a promise, I recommend you to add the catch outside csData and add it to the promise chain you have before.