(Bug Fix) isDate function: Add validation for delimiter and length ch…

…ecks to prevent undefined errors

src/lib/isDate.js

@@ -1,8 +1,8 @@
 import merge from "./util/merge";
 
 const default_date_options = {
-  format: "YYYY/MM/DD",
-  delimiters: ["/", "-"],
+  format: 'YYYY/MM/DD',
+  delimiters: ['/', '-'],
   strictMode: false,
 };
 
@@ -24,13 +24,13 @@ function zip(date, format) {
 }
 
 export default function isDate(input, options) {
-  if (typeof options === "string") {
+  if (typeof options === 'string') {
     // Allow backward compatibility for old format isDate(input [, format])
     options = merge({ format: options }, default_date_options);
   } else {
     options = merge(options, default_date_options);
   }
-  if (typeof input === "string" && isValidFormat(options.format)) {
+  if (typeof input === 'string' && isValidFormat(options.format)) {
     // Ensure the input contains at least one valid delimiter
     const hasValidDelimiter = options.delimiters.some((delimiter) =>
       input.includes(delimiter)
@@ -69,7 +69,7 @@ export default function isDate(input, options) {
     let fullYear = dateObj.y;
 
     // Check if the year starts with a hyphen
-    if (fullYear.startsWith("-")) {
+    if (fullYear.startsWith('-')) {
       return false; // Hyphen before year is not allowed
     }
 
@@ -108,8 +108,7 @@ export default function isDate(input, options) {
 
   if (!options.strictMode) {
     return (
-      Object.prototype.toString.call(input) === "[object Date]" &&
-      isFinite(input)
+       Object.prototype.toString.call(input) === '[object Date]' && isFinite(input)
     );
   }