The week of the year corresponding to the return date

Returns the zero index week of the year corresponding to the date .

• Use Date Constructor and Date.prototype.getFullYear() Get the first day of the year as Date object .
• Use Date.prototype.setDate(),Date.prototype.getDate() and Date.prototype.getDay() And mold ( %) Operator to get the first Monday of the year .
• Subtract the first Monday of the year from the given value ,date Then divide by the number of milliseconds in a week .
• be used for Math.round() Get corresponding to the given Zero index week of the year date.
• -0 If a given date Before the first Monday of the year , Then return to .

  const weekOfYear = date => {
    const startOfYear = new Date(date.getFullYear(), 0, 1);
    startOfYear.setDate(startOfYear.getDate() + (startOfYear.getDay() % 7));
    return Math.round((date - startOfYear) / (7 * 24 * 3600 * 1000));
  };
  weekOfYear(new Date('2021-06-18')); // 23