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// Format datetime <input> value in the same way as we do for
// the overflow/underflow/step mismatch validation messages.
function formatDateTimeForValidityMessage(value, inputType) {
let date;
if (inputType === "week") {
let parts = value.split("-W");
console.assert(parts.length === 2, "invalid week value: " + value);
let year = parts[0];
let weekNumber = parseInt(parts[1]);
let jan1 = new Date(year + "-01-01T00:00:00");
// the day of January corresponding to year-W1-Thursday
let dayOfW1 = ((11 - jan1.getDay()) % 7) + 1;
// Date corresponding to year-W1-Thursday
let w1Day1 = new Date(`${year}-01-0${dayOfW1}T00:00:00`);
// we use the Monday of the week for the validity message
let dayOffset = -3;
let dayOfYear = 7 * (weekNumber - 1) + dayOffset;
date = new Date(w1Day1.getTime() + 1000 * 60 * 60 * 24 * dayOfYear);
} else if (inputType === "time") {
// add arbitrary day so Date constructor is happy
date = new Date("2000-01-01T" + value);
} else if (inputType === "date") {
// add arbitrary time so Date constructor uses local time instead of UTC
date = new Date(value + "T00:00:00");
} else if (inputType === "month") {
date = new Date(value + "-01T00:00:00");
} else {
date = new Date(value);
}
let timeOptions = {
hour: "2-digit",
minute: "2-digit",
};
if (date.getSeconds()) {
timeOptions.second = "2-digit";
}
if (date.getMilliseconds()) {
timeOptions.second = "2-digit";
timeOptions.fractionalSecondDigits = 3;
}
let options = {
"datetime-local": {
year: "numeric",
month: "2-digit",
day: "2-digit",
...timeOptions,
},
month: {
year: "numeric",
month: "2-digit",
},
date: {
year: "numeric",
month: "2-digit",
day: "2-digit",
},
time: timeOptions,
};
options.week = options.date;
console.assert(
options[inputType],
"Invalid datetime input type: " + inputType
);
return date.toLocaleString(undefined, options[inputType]);
}