refactor: shift to a wildcardMatch option on the keys list type to im…

…prove behavior and allow improved control over matched keys

src/json2csv.ts

@@ -172,40 +172,51 @@ export const Json2Csv = function(options: FullJson2CsvOptions) {
         });
     }
 
+    function extractWildcardMatchKeys() {
+        if (!options.keys) return [];
+
+        return options.keys.flatMap(item => {
+            if (typeof item === 'string') {
+                // Exclude plain strings that were passed in options.keys
+                return [];
+            } else if (item?.wildcardMatch) {
+                // Return "field" value for objects with wildcardMatch: true
+                return item.field;
+            } 
+            // Exclude other objects
+            return [];
+        });
+    }
+
     /**
      * Retrieve the headings for all documents and return it.
      * This checks that all documents have the same schema.
      */
     function retrieveHeaderFields(data: object[]) {
+        const wildcardMatchKeys = extractWildcardMatchKeys();
         const keyStrings = convertKeysToHeaderFields();
         const fieldNames = getFieldNameList(data);
         const processed = processSchemas(fieldNames);
 
         if (options.keys) {
             options.keys = keyStrings;
 
-            const detectedKeysMatchingProvidedKeys = keyStrings.flatMap((userProvidedKey) => {
+            const matchedKeys = keyStrings.flatMap((userProvidedKey) => {
+                // If this is not a wildcard matched key, then just return and include it in the resulting key list
+                if (!wildcardMatchKeys.includes(userProvidedKey)) {
+                    return userProvidedKey;
+                }
+
+                // Otherwise, identify all detected keys that match with the provided wildcard key:
+                const matches = [];
                 const regex = new RegExp(`^${userProvidedKey}`);
-                const matchedKeys = [];
-
+
                 for (const detectedKey of processed) {
                     if (userProvidedKey === detectedKey || detectedKey.match(regex)) {
-                        matchedKeys.push(detectedKey);
+                        matches.push(detectedKey);
                     }
                 }
-                return matchedKeys;
-            });
-
-            const matchedKeys = Array.from(new Set(detectedKeysMatchingProvidedKeys));
-
-            keyStrings.forEach((providedKey) => {
-                const regex = new RegExp(`^${providedKey}`);
-                const anyMatch = utils.anyKeysMatch(matchedKeys, regex);
-
-                if (!anyMatch) {
-                    matchedKeys.push(providedKey);
-                }
-
+                return matches;
             });
 
             if (!options.unwindArrays) {

src/types.ts

@@ -12,6 +12,7 @@ interface DelimiterOptions {
 export type KeysList = (string | {
   field: string;
   title?: string;
+  wildcardMatch?: boolean;
 })[];
 
 interface SharedConverterOptions {