Added useDateIso8601Format (#169)

* Update json2csv.js

added useDateIso960Format

* Update converter.d.ts

added useDateIso8601Format

* Update json2csv.js

tweaked to avoid calling isDate twice

Author: adivated

src/converter.d.ts

@@ -82,6 +82,12 @@ export interface IFullOptions extends ISharedOptions {
    */
   useLocaleFormat?: boolean;
 
+  /**
+   * Should dates be output in ISO 8601 "Z" format:
+   * @default false
+   */
+   useDateIso8601Format?: boolean;
+
 }
 
 export function json2csv(data: object[],

src/json2csv.js

@@ -272,12 +272,15 @@ const Json2Csv = function(options) {
      * @returns {*}
      */
     function recordFieldValueToString(fieldValue) {
-        if (Array.isArray(fieldValue) || utils.isObject(fieldValue) && !utils.isDate(fieldValue)) {
+        const isD = utils.isDate(fieldValue); // store to avoid checking twice
+        if (Array.isArray(fieldValue) || utils.isObject(fieldValue) && !isD) {
             return JSON.stringify(fieldValue);
         } else if (utils.isUndefined(fieldValue)) {
             return 'undefined';
         } else if (utils.isNull(fieldValue)) {
             return 'null';
+        } else if (isD && options.useDateIso8601Format) {
+            return new Date(fieldValue).toISOString();
         } else {
             return !options.useLocaleFormat ? fieldValue.toString() : fieldValue.toLocaleString();
         }