tessl/npm-cron-parser

Node.js library for parsing crontab instructions with timezone support, DST handling, and iterator capabilities

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Cron Parser

Name: tessl/npm-cron-parser
Author: tessl

A comprehensive JavaScript/TypeScript library for parsing and manipulating cron expressions. Features timezone support, DST (Daylight Saving Time) handling, iterator capabilities, and extended cron syntax including special characters like L (last day), # (nth occurrence), and H (hash/random).

Package Information

Package Name: cron-parser
Package Type: npm
Language: TypeScript
Installation: npm install cron-parser

Core Imports

import { CronExpressionParser } from "cron-parser";

For named imports:

import { 
  CronExpressionParser, 
  CronExpression, 
  CronDate, 
  CronFileParser 
} from "cron-parser";

For CommonJS:

const { CronExpressionParser, CronExpression, CronDate } = require("cron-parser");

Basic Usage

import { CronExpressionParser } from "cron-parser";

try {
  // Parse a cron expression
  const interval = CronExpressionParser.parse('*/2 * * * *');
  
  // Get next execution time
  console.log('Next:', interval.next().toString());
  
  // Get next 3 execution times
  console.log('Next 3:', interval.take(3).map(date => date.toString()));
  
  // Check if a specific date matches
  console.log('Matches now:', interval.includesDate(new Date()));
  
  // Convert back to cron string
  console.log('Expression:', interval.stringify());
} catch (err) {
  console.log('Error:', err.message);
}

Architecture

Cron Parser is built around several key components:

Expression Parser: CronExpressionParser class for parsing cron strings into structured objects
Expression Object: CronExpression class for iteration, validation, and date matching
Date Wrapper: CronDate class providing timezone-aware date operations with DST support
Field System: Individual field classes (CronSecond, CronMinute, etc.) with validation and constraints
File Parser: CronFileParser for parsing complete crontab files with variables and expressions
Special Syntax: Extended support for L (last), # (nth), H (hash/random), and predefined expressions

Capabilities

Expression Parsing

Core functionality for parsing cron expressions with extensive syntax support, validation, and configuration options.

class CronExpressionParser {
  static parse(expression: string, options?: CronExpressionOptions): CronExpression;
}

interface CronExpressionOptions {
  currentDate?: Date | string | number | CronDate;
  endDate?: Date | string | number | CronDate;
  startDate?: Date | string | number | CronDate;
  tz?: string;
  expression?: string;
  hashSeed?: string;
  strict?: boolean;
}

enum PredefinedExpressions {
  '@yearly' = '0 0 0 1 1 *',
  '@annually' = '0 0 0 1 1 *',
  '@monthly' = '0 0 0 1 * *',
  '@weekly' = '0 0 0 * * 0',
  '@daily' = '0 0 0 * * *',
  '@hourly' = '0 0 * * * *',
  '@minutely' = '0 * * * * *',
  '@secondly' = '* * * * * *',
  '@weekdays' = '0 0 0 * * 1-5',  
  '@weekends' = '0 0 0 * * 0,6'
}

Expression Parsing

Schedule Iteration

Iteration capabilities for finding next/previous execution times, checking date ranges, and iterating through scheduled times.

class CronExpression {
  next(): CronDate;
  prev(): CronDate;
  hasNext(): boolean;
  hasPrev(): boolean;
  take(limit: number): CronDate[];
  reset(newDate?: Date | CronDate): void;
  includesDate(date: Date | CronDate): boolean;
  [Symbol.iterator](): Iterator<CronDate>;
}

Schedule Iteration

Date Operations

Timezone-aware date operations with automatic DST handling and cron-specific functionality.

class CronDate {
  constructor(timestamp?: CronDate | Date | number | string, tz?: string);
  
  // Standard date methods
  getTime(): number;
  getFullYear(): number;
  getMonth(): number;
  getDate(): number;
  getDay(): number;
  getHours(): number;
  getMinutes(): number;
  getSeconds(): number;
  getMilliseconds(): number;
  
  // Date manipulation
  addYear(): void;
  addMonth(): void;
  addDay(): void;
  addHour(): void;
  addMinute(): void;
  addSecond(): void;
  
  // Cron-specific functionality
  isLastDayOfMonth(): boolean;
  isLastWeekdayOfMonth(): boolean;
}

enum TimeUnit {
  Second = 'Second',
  Minute = 'Minute', 
  Hour = 'Hour',
  Day = 'Day',
  Month = 'Month',
  Year = 'Year'
}

Date Operations

Field System

Individual cron field classes with validation, constraints, and special character support for building custom expressions.

class CronFieldCollection {
  constructor(fields: CronFields);
  
  readonly second: CronSecond;
  readonly minute: CronMinute;
  readonly hour: CronHour;
  readonly dayOfMonth: CronDayOfMonth;
  readonly month: CronMonth;
  readonly dayOfWeek: CronDayOfWeek;
  
  stringify(includeSeconds?: boolean): string;
  serialize(): SerializedCronFields;
}

interface CronFields {
  second: CronSecond;
  minute: CronMinute;
  hour: CronHour;
  dayOfMonth: CronDayOfMonth;
  month: CronMonth;
  dayOfWeek: CronDayOfWeek;
}

Field System

File Parsing

Parse complete crontab files with variable extraction, expression parsing, and error handling for system administration tasks.

class CronFileParser {
  static parseFile(filePath: string): Promise<CronFileParserResult>;
  static parseFileSync(filePath: string): CronFileParserResult;
}

interface CronFileParserResult {
  variables: { [key: string]: string };
  expressions: CronExpression[];
  errors: { [key: string]: unknown };
}

File Parsing

Types

// Range types for field values
type SixtyRange = 0 | 1 | 2 | ... | 59;  // 0-59 inclusive
type HourRange = 0 | 1 | 2 | ... | 23;   // 0-23 inclusive  
type DayOfMonthRange = 1 | 2 | 3 | ... | 31 | 'L';  // 1-31 inclusive + 'L'
type MonthRange = 1 | 2 | 3 | ... | 12;  // 1-12 inclusive
type DayOfWeekRange = 0 | 1 | 2 | ... | 7 | 'L';    // 0-7 inclusive + 'L'

// Special characters and constraints
type CronChars = 'L'; // 'W' is defined in types but not currently implemented
type CronMin = 0 | 1;
type CronMax = 7 | 12 | 23 | 31 | 59;

interface CronConstraints {
  min: CronMin;
  max: CronMax;
  chars: readonly CronChars[];
  validChars: RegExp;
}

// Field serialization
interface SerializedCronField {
  wildcard: boolean;
  values: (number | string)[];
}

interface SerializedCronFields {
  second: SerializedCronField;
  minute: SerializedCronField;
  hour: SerializedCronField;
  dayOfMonth: SerializedCronField;
  month: SerializedCronField;
  dayOfWeek: SerializedCronField;
}

Install with Tessl CLI

npx tessl i tessl/npm-cron-parser

Workspace: tessl
Visibility: Public
Created: 6 months ago
Last updated: about 1 month ago
Describes: pkg:npm/cron-parser@5.3.x
Publish Source: CLI
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