Is currently during working hours (Javascript)

is-working-hours.js

// Example config for 9-5, M-F, PST (US)
var config = {
  0: {
    open: 1,
    close: 0
  },
  1: {
    open: 9,
    close: 17
  },
  2: {
    open: 9,
    close: 17
  },
  3: {
    open: 9,
    close: 17
  },
  4: {
    open: 9,
    close: 17
  },
  5: {
    open: 9,
    close: 17
  },
  6: {
    open: 1,
    close: 0
  },
  offset: -7
};

Date.prototype.subHours = function (h) {    
   this.setTime(this.getTime() - (h * 60 * 60 * 1000));
   return this;   
}

function isWorkingHour (now) {
  // Adjust remote user's time to match business time
  now = now.subHours(config.offset + (now.getTimezoneOffset() / 60));
  var day = now.getDay();
  var hours = now.getHours();
  // console.log(day, hours, config[day].open, config[day].close, config.offset);
  return hours >= config[day].open && hours < config[day].close;
}

console.log(isWorkingHour(new Date()));

Here's an adaptation, that adds support for 'exception' days that may have different working hours, with also support for MINUTES in working hour durations (so you can say the business is open from 9:30am instead of 9am):

  var config = {
    0: { open: 0, close: 0 }, // SUNDAY
    1: { open: 9, close: 17.5 },
    2: { open: 9, close: 17.5 },
    3: { open: 9, close: 17.5 },
    4: { open: 9, close: 17.5 },
    5: { open: 9, close: 17.5 },
    6: { open: 0, close: 0 }, // SATURDAY
    offset: 5.5, // TIMEZONE OFFSET. 5.5 is India/IST
    exceptions: {
      "2023-07-31": { open: 0, close: 0 }, // Christmas Day
      "2023-07-04": { open: 9, close: 13 }, // Independence Day
    },
  };
  
  function isWorkingHour(now) {
    now = now.subHours(config.offset + now.getTimezoneOffset() / 60);
  
    var day = now.getDay();
    var hours = now.getHours();
    var minutes = now.getMinutes();
    var currentTime = hours + minutes / 60;
  
    // Format the date as YYYY-MM-DD
    var dateString =
      now.getFullYear() +
      "-" +
      String(now.getMonth() + 1).padStart(2, "0") +
      "-" +
      String(now.getDate()).padStart(2, "0");
  
    // Check if the date is an exception
    if (config.exceptions.hasOwnProperty(dateString)) {
      return (
        currentTime >= config.exceptions[dateString].open &&
        currentTime < config.exceptions[dateString].close
      );
    } else {
      return currentTime >= config[day].open && currentTime < config[day].close;
    }
  }
  
  console.log(isWorkingHour(new Date()));