v3.7.0

.eslintrc.js

@@ -48,7 +48,8 @@ module.exports = {
         "prettier/prettier": "error",
         "indent": [
             "error",
-            4
+            4,
+            { "SwitchCase": 1 }
         ],
         "no-restricted-syntax": ["error", "ForInStatement", "LabeledStatement", "WithStatement"],
         "object-curly-spacing": ["error", "always"],

History.md

@@ -1,3 +1,13 @@
+# v3.7.0
+
+* [ADDED] Ability to Transform Header [#287](https://github.com/C2FO/fast-csv/issues/287)
+* [ADDED] Example require and import to README [#301](https://github.com/C2FO/fast-csv/issues/301)
+* [ADDED] Added new formatting option `alwaysWriteHeaders` to always write headers even if no rows are provided [#300](https://github.com/C2FO/fast-csv/issues/300)
+* [ADDED] Appending to csv example and docs [#272](https://github.com/C2FO/fast-csv/issues/300)
+* [FIXED] Issue with duplicate headers causing dataloss, duplicate headers will can an error to be emitted. [#276](https://github.com/C2FO/fast-csv/issues/272)
+* [FIXED] Issue where an error thrown while processing rows causes stream continue to parse, causing duplicate writes or swallowed exceptions.
+
+
 # v3.6.0
 
 * [ADDED] `maxRows` option to limit the number of rows parsed. [#275](https://github.com/C2FO/fast-csv/issues/275) [#277](https://github.com/C2FO/fast-csv/pull/277) - [@cbrittingham](https://github.com/cbrittingham)

README.md

@@ -11,6 +11,20 @@ Fast-csv is library for parsing and formatting csvs or any other delimited value
 
 `npm install -S fast-csv`
 
+## Usage
+
+To use `fast-csv` in `javascript` you can require the module/
+
+```js
+const csv = require('fast-csv');
+```
+
+To import with typescript 
+
+```typescript
+import * as csv from 'fast-csv';
+```
+
 ## Documentation
 
 * [Parsing Docs](./docs/parsing.md)
@@ -55,3 +69,4 @@ MIT <https://github.com/C2FO/fast-csv/raw/master/LICENSE>
 * Website: <http://c2fo.com>
 * Twitter: [http://twitter.com/c2fo](http://twitter.com/c2fo) - 877.465.4045
 
+

benchmark/index.js

@@ -28,7 +28,7 @@ const benchmarkFastCsv = type => num => {
     const file = path.resolve(__dirname, `./assets/${num}.${type}.csv`);
     const stream = fs
         .createReadStream(file)
-        .pipe(fastCsv.parse({ headers: true, maxRows: 10 }))
+        .pipe(fastCsv.parse({ headers: true }))
         .transform(data => {
             const ret = {};
             ['first_name', 'last_name', 'email_address'].forEach(prop => {

docs/formatting.md

@@ -26,6 +26,7 @@
     * [`quoteColumns`](#examples-quote-columns)
     * [`quoteHeaders`](#examples-quote-headers)
     * [Transforming Rows](#examples-transforming)
+    * [Appending To A CSV](#examples-appending)
 
 <a name="options"></a>
 ## Options
@@ -52,6 +53,8 @@
   *  If there is not a headers row and you want to provide one then set to a `string[]`
       * **NOTE** If the row is an object the headers must match fields in the object, otherwise you will end up with empty fields
       * **NOTE** If there are more headers than columns then additional empty columns will be added
+* `alwaysWriteHeaders: {boolean} = false`: Set to true if you always want headers written, even if no rows are written.
+  * **NOTE** This will throw an error if headers are not specified as an array.
 * `quoteColumns: {boolean|boolean[]|{[string]: boolean} = false`
    * If `true` then columns and headers will be quoted (unless `quoteHeaders` is specified).
    * If it is an object then each key that has a true value will be quoted ((unless `quoteHeaders` is specified)
@@ -836,4 +839,88 @@ VALUE1A,VALUE2A
 VALUE1A,VALUE2A
 VALUE1A,VALUE2A
 VALUE1A,VALUE2A
+```
+
+<a name="examples-appending"></a>
+### Appending To A CSV
+
+[`examples/formatting/append.example.js`](../examples/formatting/append.example.js)
+
+In this example a new csv is created then appended to.
+
+```javascript
+const path = require('path');
+const fs = require('fs');
+
+const write = (filestream, rows, options) => {
+    return new Promise((res, rej) => {
+        csv.writeToStream(filestream, rows, options)
+            .on('error', err => rej(err))
+            .on('finish', () => res());
+    });
+};
+
+// create a new csv
+const createCsv = (filePath, rows) => {
+    const csvFile = fs.createWriteStream(filePath);
+    return write(csvFile, rows, { headers: true, includeEndRowDelimiter: true });
+};
+
+// append the rows to the csv
+const appendToCsv = (filePath, rows = []) => {
+    const csvFile = fs.createWriteStream(filePath, { flags: 'a' });
+    // notice how headers are set to false
+    return write(csvFile, rows, { headers: false });
+};
+
+// read the file
+const readFile = filePath => {
+    return new Promise((res, rej) => {
+        fs.readFile(filePath, (err, contents) => {
+            if (err) {
+                return rej(err);
+            }
+            return res(contents);
+        });
+    });
+};
+
+const csvFilePath = path.resolve(__dirname, 'tmp', 'append.csv');
+
+// 1. create the csv
+createCsv(csvFilePath, [
+    { a: 'a1', b: 'b1', c: 'c1' },
+    { a: 'a2', b: 'b2', c: 'c2' },
+    { a: 'a3', b: 'b3', c: 'c3' },
+])
+    .then(() => {
+        // 2. append to the csv
+        return appendToCsv(csvFilePath, [
+            { a: 'a4', b: 'b4', c: 'c4' },
+            { a: 'a5', b: 'b5', c: 'c5' },
+            { a: 'a6', b: 'b6', c: 'c6' },
+        ]);
+    })
+    .then(() => readFile(csvFilePath))
+    .then(contents => {
+        console.log(`${contents}`);
+    })
+    .catch(err => {
+        console.error(err.stack);
+        process.exit(1);
+    });
+
+
+```
+
+Expected output
+
+```
+a,b,c
+a1,b1,c1
+a2,b2,c2
+a3,b3,c3
+a4,b4,c4
+a5,b5,c5
+a6,b6,c6
 ```

docs/parsing.md

@@ -13,6 +13,7 @@
     * [First Row As Headers](#csv-parse-first-row-as-headers)
     * [Custom Headers](#csv-parse-custom-headers)
     * [Renaming Headers](#csv-parse-renaming-headers)
+    * [Transforming Headers](#csv-parse-transforming-headers)
     * [Skipping Columns](#csv-parse-skipping-columns)
     * [Ignoring Empty Rows](#csv-parse-ignoring-empty-rows)
     * [Transforming Rows](#csv-parse-transforming)
@@ -31,12 +32,16 @@
   * `"first,name",last name`
 * `escape: {string} = '"'`: The character to used tp escape quotes inside of a quoted field.
     * `i.e`: `First,"Name"' => '"First,""Name"""`
-* `headers: {boolean|string[]} = false`:
+* `headers: {boolean|string[]|(string[]) => string[])} = false`:
   *  If you want the first row to be treated as headers then set to `true`
   *  If there is not a headers row and you want to provide one then set to a `string[]`
   *  If you wish to discard the first row and use your own headers set to a `string[]` and set the `renameHeaders` option to `true`
-* `renameHeaders: {boolean} = false`: If you want the first line of the file to be removed and replaced by the one provided in the `headers` option.
+  *  If you wish to transform the headers you can provide a transform function. 
+      *  **NOTE** This will always rename the headers
+  * **NOTE** If headers either parsed, provided or transformed are NOT unique, then an error will be emitted and the stream will stop parsing.
+* `renameHeaders: {boolean} = false`: If you want the first line of the file to be removed and replaced by the one provided in the `headers` option. 
   * **NOTE** This option should only be used if the `headers` option is a `string[]`
+  * **NOTE** If the `headers` option is a function then this option is always set to true.
 * `ignoreEmpty: {boolean} = false`: If you wish to ignore empty rows.
   * **NOTE** this will discard columns that are all white space or delimiters.
 * `comment: {string} = null`: If your CSV contains comments you can use this option to ignore lines that begin with the specified character (e.g. `#`).
@@ -337,6 +342,39 @@ Expected output
 Parsed 2 rows
 ```
 
+<a name="csv-parse-transforming-headers"></a>
+### Transforming Headers
+
+If the CSV contains a header row but you want transform the headers you can provide a function to the `headers` option.
+
+[`examples/parsing/rename_headers.example.js`](../examples/parsing/rename_headers.example.js)
+
+```javascript
+const { EOL } = require('os');
+
+const CSV_STRING = ['header1,header2', 'a1,b1', 'a2,b2'].join(EOL);
+
+const stream = csv
+    .parse({
+        headers: headers => headers.map(h => h.toUpperCase()),
+    })
+    .on('error', error => console.error(error))
+    .on('data', row => console.log(row))
+    .on('end', rowCount => console.log(`Parsed ${rowCount} rows`));
+
+stream.write(CSV_STRING);
+stream.end();
+
+```
+
+Expected output
+
+```
+{ HEADER1: 'a1', HEADER2: 'b1' }
+{ HEADER1: 'a2', HEADER2: 'b2' }
+Parsed 2 rows
+```
+
 <a name="csv-parse-skipping-columns"></a>
 ### Skipping Columns
 
@@ -711,3 +749,4 @@ Parsed 4 rows
 ```
 
 
+

examples/formatting/append.example.js

@@ -0,0 +1,61 @@
+const path = require('path');
+const fs = require('fs');
+const csv = require('../..');
+
+const write = (filestream, rows, options) => {
+    return new Promise((res, rej) => {
+        csv.writeToStream(filestream, rows, options)
+            .on('error', err => rej(err))
+            .on('finish', () => res());
+    });
+};
+
+// create a new csv
+const createCsv = (filePath, rows) => {
+    const csvFile = fs.createWriteStream(filePath);
+    return write(csvFile, rows, { headers: true, includeEndRowDelimiter: true });
+};
+
+// append the rows to the csv
+const appendToCsv = (filePath, rows = []) => {
+    const csvFile = fs.createWriteStream(filePath, { flags: 'a' });
+    // notice how headers are set to false
+    return write(csvFile, rows, { headers: false });
+};
+
+// read the file
+const readFile = filePath => {
+    return new Promise((res, rej) => {
+        fs.readFile(filePath, (err, contents) => {
+            if (err) {
+                return rej(err);
+            }
+            return res(contents);
+        });
+    });
+};
+
+const csvFilePath = path.resolve(__dirname, 'tmp', 'append.csv');
+
+// 1. create the csv
+createCsv(csvFilePath, [
+    { a: 'a1', b: 'b1', c: 'c1' },
+    { a: 'a2', b: 'b2', c: 'c2' },
+    { a: 'a3', b: 'b3', c: 'c3' },
+])
+    .then(() => {
+        // 2. append to the csv
+        return appendToCsv(csvFilePath, [
+            { a: 'a4', b: 'b4', c: 'c4' },
+            { a: 'a5', b: 'b5', c: 'c5' },
+            { a: 'a6', b: 'b6', c: 'c6' },
+        ]);
+    })
+    .then(() => readFile(csvFilePath))
+    .then(contents => {
+        console.log(`${contents}`);
+    })
+    .catch(err => {
+        console.error(err.stack);
+        process.exit(1);
+    });

examples/parsing/transform_headers.example.js

@@ -0,0 +1,15 @@
+const { EOL } = require('os');
+const csv = require('../../');
+
+const CSV_STRING = ['header1,header2', 'a1,b1', 'a2,b2'].join(EOL);
+
+const stream = csv
+    .parse({
+        headers: headers => headers.map(h => h.toUpperCase()),
+    })
+    .on('error', error => console.error(error))
+    .on('data', row => console.log(row))
+    .on('end', rowCount => console.log(`Parsed ${rowCount} rows`));
+
+stream.write(CSV_STRING);
+stream.end();