Get datetime with forma ISO 8601 in javascript

iso8601.js

const getTimeZone = ()=>{
  
  let timezone_offset_min = new Date().getTimezoneOffset(),
    offset_hrs = parseInt(Math.abs(timezone_offset_min/60)),
    offset_min = Math.abs(timezone_offset_min%60),
    timezone_standard;

  if(offset_hrs < 10)
    offset_hrs = '0' + offset_hrs;

  if(offset_min < 10)
    offset_min = '0' + offset_min;

  // Add an opposite sign to the offset
  // If offset is 0, it means timezone is UTC
  if(timezone_offset_min < 0)
    timezone_standard = '+' + offset_hrs + ':' + offset_min;
  else if(timezone_offset_min > 0)
    timezone_standard = '-' + offset_hrs + ':' + offset_min;
  else if(timezone_offset_min == 0)
    timezone_standard = 'Z';

    return timezone_standard;

}

const datetime = ()=>{
  
  let dt = new Date(),  
  current_date = dt.getDate(),
  current_month = dt.getMonth() + 1,
  current_year = dt.getFullYear(),
  current_hrs = dt.getHours(),
  current_mins = dt.getMinutes(),
  current_secs = dt.getSeconds(),
  current_datetime;

  // Add 0 before date, month, hrs, mins or secs if they are less than 0
  current_date = current_date < 10 ? '0' + current_date : current_date;
  current_month = current_month < 10 ? '0' + current_month : current_month;
  current_hrs = current_hrs < 10 ? '0' + current_hrs : current_hrs;
  current_mins = current_mins < 10 ? '0' + current_mins : current_mins;
  current_secs = current_secs < 10 ? '0' + current_secs : current_secs;

  // Current datetime
  // String such as 2016-07-16T19:20:30
  current_datetime = current_year + '-' + current_month + '-' + current_date + 'T' + current_hrs + ':' + current_mins + ':' + current_secs;

  return current_datetime;

}

const iso8601 = ()=> datetime()+getTimeZone();