fix: ensure values are strings when passed to the functions

index.js

@@ -18,6 +18,19 @@ const rules = {
 
 /* eslint-enable no-control-regex */
 
+/**
+ * Ensure the value is a string.
+ * @private
+ * @param s {any} the value to be checked
+ * @throws {TypeError} if the value is not a string
+ */
+const assertString = (s) => {
+  const t = typeof s;
+  if (t !== 'string') {
+    throw new TypeError('Value must be a string');
+  }
+};
+
 /**
  * Minimal, RFC 6749, compliant unicode validator.
  * @see https://datatracker.ietf.org/doc/html/rfc6749#appendix-A
@@ -33,6 +46,7 @@ const isFormat = {
    */
 
   nchar: function(value) {
+    assertString(value);
     return rules.NCHAR.test(value);
   },
 
@@ -45,6 +59,7 @@ const isFormat = {
    */
 
   nqchar: function(value) {
+    assertString(value);
     return rules.NQCHAR.test(value);
   },
 
@@ -57,6 +72,7 @@ const isFormat = {
    */
 
   nqschar: function(value) {
+    assertString(value);
     return rules.NQSCHAR.test(value);
   },
 
@@ -70,6 +86,7 @@ const isFormat = {
    */
 
   uchar: function(value) {
+    assertString(value);
     // manually test \u10000-\u10FFFF
     if (rules.UNICODECHARNOCRLF.test(value)) {
       return true;
@@ -86,6 +103,7 @@ const isFormat = {
    * @return {boolean} true, if valid, otherwise false
    */
   uri: function(value) {
+    assertString(value);
     return rules.URI.test(value);
   },
 
@@ -98,6 +116,7 @@ const isFormat = {
    */
 
   vschar: function(value) {
+    assertString(value);
     return rules.VSCHAR.test(value);
   }
 };