Rename js snippets

snippets/js/s/json-to-csv.md

@@ -0,0 +1,41 @@
+---
+title: JSON to CSV
+type: snippet
+language: javascript
+tags: [array,string,object]
+cover: pink-flowers
+dateModified: 2021-10-13T19:29:39+02:00
+---
+
+Converts an array of objects to a comma-separated values (CSV) string that contains only the `columns` specified.
+
+- Use `Array.prototype.join()` to combine all the names in `columns` to create the first row, using the provided `delimiter`.
+- Use `Array.prototype.map()` and `Array.prototype.reduce()` to create a row for each object. Substitute non-existent values with empty strings and only mapping values in `columns`.
+- Use `Array.prototype.join()` to combine all rows into a string, separating each row with a newline (`\n`).
+- 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"'
+```