Been knocking my head for a few hours searching for a solution. Why would prevDate return undefined? Just don't understand what I am missing.
async function prevDate(date) {
date.setDate(date.getDate()-1)
if (date.getDay() == 0 || date.getDay() == 6) {
prevDate(date)
} else {
console.log("date: ", date, "day: ", date.getDay())
return (date)
}
}
date = new Date("2021-09-20T00:00:00")
prevDate(date)
.then((res) => {
console.log("res: ", res) //undefined
})
.catch((err) => {
console.log(err)
})
output
date: 2021-09-17T04:00:00.000Z day: 5
res: undefined
The other people stated the reason your code doesn't work. But I'm wondering why you are using an async function for code that is not asynchronous. If you still want to use a recursive function it can be simply written like this:
function prevDate (date) {
date.setDate(date.getDate() - 1);
if (!(date.getDay() % 6)) {
return prevDate(date);
} else {
console.log(`date: ${date} day: ${date.getDay()}`);
return date;
}
}
const date = new Date("2021-09-20T00:00:00");
console.log(`res: ${prevDate(date)}`);Or you can simplify it even further:
const prevDate = (date) => {
date.setDate(date.getDate() - 1);
return !(date.getDay() % 6) ? prevDate(date) : date;
};
const date = new Date("2021-09-20T00:00:00");
console.log(`res: ${prevDate(date)}`);You can write a simple function that subtracts 1, 2 or 3 days depending on which day of the week the date is on, e.g.
// Return previous work day (i.e. not Sat or Sun)
function getPreviousWorkDay(d = new Date()) {
return new Date(d.getFullYear(), d.getMonth(), d.getDate() - ({1:3, 0:2}[d.getDay()] || 1)
);
}
// Examples over year and month end
[new Date(2020,11,28), // Mon
new Date(2020,11,29), // Tue
new Date(2020,11,30), // Wed
new Date(2020,11,31), // Thu
new Date(2021, 0, 1), // Fri
new Date(2021, 0, 2), // Sat
new Date(2021, 0, 3), // Sun
].forEach(d =>
console.log(`${d.toDateString()} => ${getPreviousWorkDay(d).toDateString()}`)
);