Cron एक्सप्रेशन पार्सर और बिल्डर - Crontab Guru विकल्प

// Simple cron expression parser
function parseCronExpression(expression) {
  const parts = expression.trim().split(/\s+/);
  if (parts.length !== 5) {
    throw new Error('Invalid cron expression: expected 5 fields');
  }

  const [minute, hour, dayOfMonth, month, dayOfWeek] = parts;

  function parseField(field, min, max) {
    if (field === '*') {
      return Array.from({ length: max - min + 1 }, (_, i) => min + i);
    }
    const values = new Set();
    field.split(',').forEach(part => {
      if (part.includes('/')) {
        const [range, step] = part.split('/');
        const stepNum = parseInt(step, 10);
        let start = min, end = max;
        if (range !== '*' && range.includes('-')) {
          [start, end] = range.split('-').map(Number);
        }
        for (let i = start; i <= end; i += stepNum) values.add(i);
      } else if (part.includes('-')) {
        const [start, end] = part.split('-').map(Number);
        for (let i = start; i <= end; i++) values.add(i);
      } else {
        values.add(parseInt(part, 10));
      }
    });
    return Array.from(values).sort((a, b) => a - b);
  }

  return {
    minute: parseField(minute, 0, 59),
    hour: parseField(hour, 0, 23),
    dayOfMonth: parseField(dayOfMonth, 1, 31),
    month: parseField(month, 1, 12),
    dayOfWeek: parseField(dayOfWeek, 0, 6),
  };
}

// Example usage
const expr = '0 9 * * 1-5';
console.log('Parsed:', parseCronExpression(expr));