I'm trying to synchronize calendars, but the receiving server only wants "bite-sized" data, so I decided to sync PER USER PER MONTH.
Thus, I made a double loop:
First I loop through all users, and within that loop, I loop through the months if the date-range spans multiple months.
However, because the sync function is asynchronous, it executes multiple resources and months at the same time, because the loop doesn't wait for completion.
I know similar questions have been asked before, but for some reason I just cannot get it to work.
Here are my functions:
function loopThroughMonths(resourceIds, startDate, endDate) {
startDateObject = new Date(startDate);
endDateObject = new Date(endDate);
// Check how many months our date range spans:
var dateRangeMonths = monthDiff(startDateObject, endDateObject);
if (dateRangeMonths > 0) {
// Loop through each month
for (let i = 0; i <= dateRangeMonths; i++) {
if (i == 0) {
// For the first month, the starting date is equal to the start of the date range
var loopStartDate = startDate;
var loopEndDate = formatDate(
lastDayOfMonth(
startDateObject.getFullYear(),
startDateObject.getMonth(),
),
);
}
if (i != 0 && i != dateRangeMonths) {
var loopMonth = new Date(
startDateObject.getFullYear(),
startDateObject.getMonth() + i,
1,
);
var loopStartDate = formatDate(
firstDayOfMonth(loopMonth.getFullYear(), loopMonth.getMonth()),
);
var loopEndDate = formatDate(
lastDayOfMonth(loopMonth.getFullYear(), loopMonth.getMonth()),
);
}
if (i == dateRangeMonths) {
// For the last month, the end date is equal to the last date of the date range.
var loopStartDate = formatDate(
firstDayOfMonth(
endDateObject.getFullYear(),
endDateObject.getMonth(),
),
);
var loopEndDate = endDate;
}
loopThroughResources(resourceIds, 0, loopStartDate, loopEndDate);
}
} else {
// Date range falls within 1 month, just proceed to looping through resources
loopThroughResources(resourceIds, 0, startDate, endDate);
}
}
function loopThroughResources(resourceIds, i, loopStartDate, loopEndDate) {
if (i == resourceIds.length) {
$("#start_exchange")
.text("Synchroniseren")
.removeAttr("disabled")
.css("cursor", "pointer");
return;
}
var resourceId = resourceIds[i];
$("#exchange_output").append(
"Start synchroniseren naar Outlook-agenda van " +
resourceNames.get(resourceId) +
" van " +
loopStartDate +
" tot " +
loopEndDate +
"...<br>",
);
$.post(
"sync.php",
{
resourceId: resourceId,
startDate: loopStartDate,
endDate: loopEndDate,
},
function (response) {
$("#exchange_output").append(response);
i = i + 1;
loopThroughResources(resourceIds, i, loopStartDate, loopEndDate);
},
);
}
So to explain:
loopThroughMonths first checks if startDate and endDate differ more than 0 months. If so, it looks through each month. If not, it just immediately executes loopThroughResources.
In case the dateRangeMonths spans multiple months, we loop through them using a for loop and perform the loopThroughResources function for every month.
Thus, if we say:
Synchronise resources A, B, C from 2023-12-27 till 2024-02-16
It will do:
Sync 2023-12-27 till 2023-12-31 (part of december 2023) for resource A
Sync 2023-12-27 till 2023-12-31 (part of december 2023) for resource B
Sync 2023-12-27 till 2023-12-31 (part of december 2023) for resource C
Sync 2024-01-01 till 2024-01-31 (whole january 2023) for resource A
Sync 2024-01-01 till 2024-01-31 (whole january 2023) for resource B
Sync 2024-01-01 till 2024-01-31 (whole january 2023) for resource C
Sync 2024-02-01 till 2024-02-16 (part of february 2023) for resource A
Sync 2024-02-01 till 2024-02-16 (part of february 2023) for resource B
Sync 2024-02-01 till 2024-02-16 (part of february 2023) for resource C
The code works, but it is not waiting for all resources to complete (i.e. before the loopThroughResources function is done) before moving on to the next month.
For the resources, I even made it so that it waits until syncing resource A is complete before it proceeds to resource B, by calling the function from the $.post complete function, but I basically need another wait for the ENTIRE loopThroughResources function (and I'm guessing it needs to be something with Promises.all...)
I know I have to do something with promises, but I just can't get it to work.... Any help would be greatly appreciated.
You'll have a better time if you separate the concerns of what you want to do and doing it:
function toDate(start) {
return start.toISOString().split("T")[0];
}
function getFirstAndLastDayOfMonth(date) {
let start = new Date(date);
let end = new Date(date);
end.setMonth(end.getMonth() + 1);
end.setDate(0);
return {
start: toDate(start),
end: toDate(end),
};
}
function getDateRanges(startDate, endDate) {
let startDateObject = new Date(startDate);
let endDateObject = new Date(endDate);
let ranges = [];
let date = new Date(startDateObject);
date.setDate(15);
while (date < endDateObject) {
ranges.push(getFirstAndLastDayOfMonth(date));
date.setMonth(date.getMonth() + 1);
}
// Adjust start and end
ranges[0].start = toDate(startDateObject);
ranges[ranges.length - 1].end = toDate(endDateObject);
return ranges;
}
function getSyncJobs(resourceIds, startDate, endDate) {
const jobs = [];
const ranges = getDateRanges(startDate, endDate);
for (let resourceId of resourceIds) {
for (let range of ranges) {
jobs.push({
resourceId,
startDate: range.start,
endDate: range.end,
});
}
}
return jobs;
}
function doJob(params, done) {
// (do $.post here instead of `setTimeout`...)
console.log(params);
setTimeout(done, 500);
}
function go(done) {
// Build a queue of sync jobs we consume in `doNextJob`
const syncJobs = getSyncJobs(
["A", "B", "C"],
"2023-12-27",
"2024-02-16",
);
function doNextJob() {
console.log(`Remaining jobs: ${syncJobs.length}`);
if (syncJobs.length === 0) {
return done();
}
const job = syncJobs.shift();
doJob(job, doNextJob);
}
doNextJob();
}
go(function () {
console.log("All done!");
});If you can promisify $.post into something you can await, you can get rid of the callbacks altogether and the execution becomes just
async function doJob(job) {
console.log(job);
await new Promise(resolve => setTimeout(resolve, 500));
}
async function go() {
// Build a queue of sync jobs
const syncJobs = getSyncJobs(
["A", "B", "C"],
"2023-12-27",
"2024-02-16",
);
for(let job of syncJobs) {
await doJob(job);
}
console.log("All done!");
}