From 7443e9270f7e5eafb949a0e6edc7ec6148a2b669 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Fri, 6 Jul 2018 20:25:46 +0300
Subject: [PATCH] Add JSONtoCSV

Resolve #686
---
 snippets/JSONtoCSV.md            | 26 ++++++++++++++++++++++++++
 snippets/arrayToCSV.md           |  4 ++--
 tag_database                     |  1 +
 test/JSONtoCSV/JSONtoCSV.js      | 11 +++++++++++
 test/JSONtoCSV/JSONtoCSV.test.js | 12 ++++++++++++
 5 files changed, 52 insertions(+), 2 deletions(-)
 create mode 100644 snippets/JSONtoCSV.md
 create mode 100644 test/JSONtoCSV/JSONtoCSV.js
 create mode 100644 test/JSONtoCSV/JSONtoCSV.test.js

diff --git a/snippets/JSONtoCSV.md b/snippets/JSONtoCSV.md
new file mode 100644
index 000000000..fac5f6946
--- /dev/null
+++ b/snippets/JSONtoCSV.md
@@ -0,0 +1,26 @@
+### JSONtoCSV
+
+Converts an array of objects to a comma-separated values (CSV) string that contains only the `columns` specified.
+
+Use `Array.join(demiliter)` to combine all the names in `columns` to create the first row.
+Use `Array.map()` and `Array.reduce()` to create a row for each object, substituting non-existent values with empty strings and only mapping values in `columns`.
+Use `Array.join('\n')` to combine all rows into a string.
+Omit the third argument, `delimiter`, to use a default delimiter of `,`.
+
+```js
+const JSONtoCSV = (arr, columns, delimiter = ',') =>
+  [
+    columns.join(delimiter),
+    ...arr.map(obj =>
+      columns.reduce(
+        (acc, key) => `${acc}${!acc.length ? '' : delimiter}"${!obj[key] ? '' : obj[key]}"`,
+        ''
+      )
+    )
+  ].join('\n');
+```
+
+```js
+JSONtoCSV([{ a: 1, b: 2 }, { a: 3, b: 4, c: 5 }, { a: 6 }, { b: 7 }], ['a', 'b']); // 'a,b\n"1","2"\n"3","4"\n"6",""\n"","7"'
+JSONtoCSV([{ a: 1, b: 2 }, { a: 3, b: 4, c: 5 }, { a: 6 }, { b: 7 }], ['a', 'b'], ';'); // 'a;b\n"1";"2"\n"3";"4"\n"6";""\n"";"7"'
+```
diff --git a/snippets/arrayToCSV.md b/snippets/arrayToCSV.md
index eecce9d99..1d65c7adf 100644
--- a/snippets/arrayToCSV.md
+++ b/snippets/arrayToCSV.md
@@ -2,8 +2,8 @@
 
 Converts a 2D array to a comma-separated values (CSV) string.
 
-Use `Array.map()` and `String.join(delimiter)` to combine individual 1D arrays (rows) into strings.
-Use `String.join('\n')` to combine all rows into a CSV string, separating each row with a newline.
+Use `Array.map()` and `Array.join(delimiter)` to combine individual 1D arrays (rows) into strings.
+Use `Array.join('\n')` to combine all rows into a CSV string, separating each row with a newline.
 Omit the second argument, `delimiter`, to use a default delimiter of `,`.
 
 ```js
diff --git a/tag_database b/tag_database
index 7663809dc..a2b57d852 100644
--- a/tag_database
+++ b/tag_database
@@ -152,6 +152,7 @@ isUndefined:type
 isUpperCase:string,utility
 isValidJSON:type,json
 join:array
+JSONtoCSV:array,string,object,advanced
 JSONToFile:node,json
 last:array
 lcm:math,recursion
diff --git a/test/JSONtoCSV/JSONtoCSV.js b/test/JSONtoCSV/JSONtoCSV.js
new file mode 100644
index 000000000..912f55338
--- /dev/null
+++ b/test/JSONtoCSV/JSONtoCSV.js
@@ -0,0 +1,11 @@
+const JSONtoCSV = (arr, columns, delimiter = ',') =>
+[
+columns.join(delimiter),
+...arr.map(obj =>
+columns.reduce(
+(acc, key) => `${acc}${!acc.length ? '' : delimiter}"${!obj[key] ? '' : obj[key]}"`,
+''
+)
+)
+].join('\n');
+module.exports = JSONtoCSV;
\ No newline at end of file
diff --git a/test/JSONtoCSV/JSONtoCSV.test.js b/test/JSONtoCSV/JSONtoCSV.test.js
new file mode 100644
index 000000000..36ec9ec2d
--- /dev/null
+++ b/test/JSONtoCSV/JSONtoCSV.test.js
@@ -0,0 +1,12 @@
+const expect = require('expect');
+const JSONtoCSV = require('./JSONtoCSV.js');
+
+test('JSONtoCSV is a Function', () => {
+  expect(JSONtoCSV).toBeInstanceOf(Function);
+});
+test('JSONtoCSV works with default delimiter', () => {
+  expect(JSONtoCSV([{ a: 1, b: 2 }, { a: 3, b: 4, c: 5 }, { a: 6 }, { b: 7 }], ['a', 'b'])).toBe('a,b\n"1","2"\n"3","4"\n"6",""\n"","7"');
+});
+test('JSONtoCSV works with custom delimiter', () => {
+  expect(JSONtoCSV([{ a: 1, b: 2 }, { a: 3, b: 4, c: 5 }, { a: 6 }, { b: 7 }], ['a', 'b'], ';')).toBe('a;b\n"1";"2"\n"3";"4"\n"6";""\n"";"7"');
+});