From 5a8b7e038b72531dbf39e6c091017ccfbfe6efc8 Mon Sep 17 00:00:00 2001
From: Guillaume <guillaumeroyer.mail@gmail.com>
Date: Sat, 15 Jan 2022 02:32:30 +0100
Subject: [PATCH] feat(json2csv): use sort function for `sortHeader` option
 (#217)

---
 README.md                            |  2 +-
 lib/converter.d.ts                   |  2 +-
 lib/json2csv.js                      |  2 +-
 test/config/testCsvFilesList.js      |  1 +
 test/data/csv/sortedHeaderCustom.csv |  3 +++
 test/json2csv.js                     | 10 ++++++++++
 6 files changed, 17 insertions(+), 3 deletions(-)
 create mode 100644 test/data/csv/sortedHeaderCustom.csv

diff --git a/README.md b/README.md
index 4d2843a..4f84c5e 100755
--- a/README.md
+++ b/README.md
@@ -96,7 +96,7 @@ Looking for examples? Check out the Wiki: [json-2-csv Wiki](https://github.com/m
     * Note: Using this option may override other options, including `useDateIso8601Format` and `useLocaleFormat`.
   * `prependHeader` - Boolean - Should the auto-generated header be prepended as the first line in the CSV?
     * Default: `true`
-  * `sortHeader` - Boolean - Should the header keys be sorted in alphabetical order? 
+  * `sortHeader` - Boolean or Function - Should the header keys be sorted in alphabetical order? or pass a function to use a custom sorting function
     * Default: `false`
   * `trimFieldValues` - Boolean - Should the field values be trimmed?
     * Default: `false`
diff --git a/lib/converter.d.ts b/lib/converter.d.ts
index 833ed5b..df9834b 100644
--- a/lib/converter.d.ts
+++ b/lib/converter.d.ts
@@ -85,7 +85,7 @@ export interface IFullOptions extends ISharedOptions {
    * Should the header keys be sorted in alphabetical order
    * @default false
    */
-  sortHeader?: boolean;
+  sortHeader?: boolean|((a: any, b: any) => number);
 
   /**
    * Should array values be "unwound" such that there is one line per value in the array?
diff --git a/lib/json2csv.js b/lib/json2csv.js
index 5d1d274..2b9c6aa 100755
--- a/lib/json2csv.js
+++ b/lib/json2csv.js
@@ -103,7 +103,7 @@ const Json2Csv = function(options) {
      */
     function sortHeaderFields(fieldNames) {
         if (options.sortHeader) {
-            return fieldNames.sort();
+            return typeof options.sortHeader === 'function' ? fieldNames.sort(options.sortHeader) : fieldNames.sort();
         }
         return fieldNames;
     }
diff --git a/test/config/testCsvFilesList.js b/test/config/testCsvFilesList.js
index 78edcb0..64d7ac6 100644
--- a/test/config/testCsvFilesList.js
+++ b/test/config/testCsvFilesList.js
@@ -27,6 +27,7 @@ const fs = require('fs'),
         {key: 'extraLine', file: '../data/csv/extraLine.csv'},
         {key: 'noHeader', file: '../data/csv/noHeader.csv'},
         {key: 'sortedHeader', file: '../data/csv/sortedHeader.csv'},
+        {key: 'sortedHeaderCustom', file: '../data/csv/sortedHeaderCustom.csv'},
         {key: 'emptyFieldValues', file: '../data/csv/emptyFieldValues.csv'},
         {key: 'quotedEmptyFieldValue', file: '../data/csv/quotedEmptyFieldValue.csv'},
         {key: 'csvEmptyLastValue', file: '../data/csv/csvEmptyLastValue.csv'},
diff --git a/test/data/csv/sortedHeaderCustom.csv b/test/data/csv/sortedHeaderCustom.csv
new file mode 100644
index 0000000..796e33b
--- /dev/null
+++ b/test/data/csv/sortedHeaderCustom.csv
@@ -0,0 +1,3 @@
+optionalField,object.subField,number,isBoolean,arrayOfStrings
+this one has it,subValue,5,true,"[""test1"",""test2""]"
+null,subValue,7,false,"[""test3"",""test4""]"
\ No newline at end of file
diff --git a/test/json2csv.js b/test/json2csv.js
index d2cebd9..22cef1d 100644
--- a/test/json2csv.js
+++ b/test/json2csv.js
@@ -328,6 +328,16 @@ function runTests(jsonTestData, csvTestData) {
                 });
             });
 
+            it('should sort the header with a custom function in the csv', (done) => {
+                converter.json2csv(jsonTestData.assortedValues, (err, csv) => {
+                    if (err) done(err);
+                    csv.should.equal(csvTestData.sortedHeaderCustom);
+                    done();
+                }, {
+                    sortHeader: (a, b) => b.localeCompare(a)
+                });
+            });
+
             it('should trim the header fields when specified', (done) => {
                 converter.json2csv(jsonTestData.trimHeader, (err, csv) => {
                     if (err) done(err);