feat: add isCronTimeValid function to validate cron expressions (#959)

README.md

@@ -179,6 +179,18 @@ day of week    0-7 (0 or 7 is Sunday, or use names)
   console.log(`The job would run in ${timeout}ms`);
   ```
 
+- `validateCronExpression`: Validates if a given cron expression is valid (returns an object with `valid` and `error` properties).
+
+  ```javascript
+  import * as cron from 'cron';
+
+  const validation = cron.validateCronExpression('0 0 * * *');
+  console.log(`Is the cron expression valid? ${validation.valid}`);
+  if (!validation.valid) {
+  	console.error(`Validation error: ${validation.error}`);
+  }
+  ```
+
 ### CronJob Class
 
 #### Constructor

examples/is_crontime_valid.js

@@ -1,9 +1,3 @@
-import { CronJob } from '../src';
+import { validateCronExpression } from '../src';
 
-try {
-	new CronJob('NOT VALID', () => {
-		console.log("shouldn't get printed");
-	});
-} catch (e) {
-	console.log('omg err', e);
-}
+console.log('is valid? ', validateCronExpression('NOT VALID').valid);

src/index.ts

@@ -20,3 +20,5 @@ export const sendAt = (cronTime: string | Date | DateTime): DateTime =>
 
 export const timeout = (cronTime: string | Date | DateTime): number =>
 	new CronTime(cronTime).getTimeout();
+
+export const validateCronExpression = CronTime.validateCronExpression;

src/time.ts

@@ -75,6 +75,23 @@ export class CronTime {
 		}
 	}
 
+	static validateCronExpression(cronExpression: string): {
+		valid: boolean;
+		error?: CronError;
+	} {
+		try {
+			new CronTime(cronExpression);
+			return {
+				valid: true
+			};
+		} catch (error: any) {
+			return {
+				valid: false,
+				error
+			};
+		}
+	}
+
 	private _getWeekDay(date: DateTime) {
 		return date.weekday === 7 ? 0 : date.weekday;
 	}

tests/crontime.test.ts

@@ -1,6 +1,7 @@
 import { DateTime } from 'luxon';
 import sinon from 'sinon';
-import { CronTime } from '../src';
+import { CronTime, validateCronExpression } from '../src';
+import { CronError } from '../src/errors';
 
 describe('crontime', () => {
 	// eslint-disable-next-line jest/no-standalone-expect
@@ -778,3 +779,35 @@ describe('crontime', () => {
 		}).toThrow();
 	});
 });
+
+describe('validateCronExpression', () => {
+	it('should return true for valid cron expressions', () => {
+		const validExpressions = [
+			'* * * * *',
+			'0 0 * * *',
+			'0 0 1 1 *',
+			'*/5 * * * *'
+		];
+
+		validExpressions.forEach(expression => {
+			const validation = validateCronExpression(expression);
+			expect(validation.valid).toBe(true);
+			expect(validation.error).toBeUndefined();
+		});
+	});
+
+	it('should return false for invalid cron expressions', () => {
+		const invalidExpressions = [
+			'* * * *',
+			'60 * * * *',
+			'* * * * * * *',
+			'invalid cron'
+		];
+
+		invalidExpressions.forEach(expression => {
+			const validation = validateCronExpression(expression);
+			expect(validation.valid).toBe(false);
+			expect(validation.error).toBeInstanceOf(CronError);
+		});
+	});
+});