如何创建一个function返回下一个指定工作日的天数js？

Question

Write a function that accepts a weekday as a string (eg 'Sunday') and returns the number of days to the next specified weekday. The input should be case-insensitive. If the specified weekday is today, return Hey, today is ${ specifiedWeekday } =) , otherwise return It's ${ number } day(s) left till ${ specifiedWeekday } . Please note, although input is case-insensitive, weekday name in the output string should be always in proper case. howFarIs('friday'); // "It's 1 day(s) left till Friday." (on October 22nd) howFarIs('Thursday'); // "Hey, today is Thursday =)" (on October 22nd)

That s what I we done, pls help me with the next steps or with the correct solution.

function howFarIs(day) {
    let test = new RegExp(`${day}`, 'gi')
    for (let day of days) { 
        if (day.match(test)) {
            var dayIndex = days.indexOf(day);
        }
    }
    
    let date = new Date();
    let todayIndex = date.getDay()
    
}

Answer 1

I don't think a RegExp is necessary for this one. You should have most of the code below. It's still needs a few adjustments here and there but most of the logic is there.

const dayLC = day.toLowerCase(); 
const daysOfTheWeek = ['sunday','monday','tuesday','etc'];
const index = daysOfTheWeek.findIndex((e) => e === dayLC);
const today = (new Date()).getDay();
if(today===index) 
{
   return `Hey, today is ${capitalize(daysOfTheWeek[today])}`;
}
else if(today<index)
{

   return `It's ${ index-today } day(s) left till ${ specifiedWeekday }`
else
{
//index < today
 return `It's ${ index-today+7 } day(s) left till ${ specifiedWeekday }`

function capitalize(word) {
    const lower = word.toLowerCase();
    return lower.charAt(0).toUpperCase() + lower.slice(1);
}

Answer 2

const days = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']

function howFarIs(dayOfWeek) {
    let test = new RegExp(`${dayOfWeek}`, 'gi')
    for (let day of days) { 
        if (day.match(test)) {
            var dayIndex = days.indexOf(day);
        }
    }

    let dayMilliseconds =
        1000 * 60 * 60 * 24;

    var resultDate = new Date(new Date().getTime());

    resultDate.setDate(new Date().getDate() + (7 + dayIndex - new Date().getDay()) % 7);

    var diff = Math.abs((new Date().getTime() - resultDate.getTime()) / (dayMilliseconds));
    if (diff == 0) {
        var result = `Hey, today is ${days[dayIndex]} =)`
    } else {
        result = `It's ${diff} day(s) left till ${days[dayIndex]}.`
    }
    return result;
}

Answer 3

const days_of_week = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];

function howFarIs(day) {
    const day_index = days_of_week.findIndex(weekday => {
      return weekday.toLowerCase() === day.toLowerCase();
    });
  
  if (day_index === -1) {
    return 'Invalid parameter entered.';
  }

    let today = new Date();
    let todayIndex = today.getDay();
  
  if (todayIndex === day_index) {
    return `Hey, today is ${days_of_week[day_index]}`;
  } else if (todayIndex > day_index) {
    var number = day_index + (7-todayIndex);
  } else {
    var number = day_index - todayIndex;
  }
  
  return `${ number } day(s) left till ${ days_of_week[day_index] }`;
}