fix: Remove callback support

BREAKING CHANGE: callback is no longer available, just return the csv from the json2csv.

- updated tests
- updated readme

Author: Ilya Radchenko

README.md

@@ -72,7 +72,6 @@ try {
   - `includeEmptyRows` - Boolean, includes empty rows. Defaults to `false`.
   - `preserveNewLinesInValues` - Boolean, preserve \r and \n in values. Defaults to `false`.
   - `withBOM` - Boolean, with BOM character. Defaults to `false`.
-- `callback` - `function (error, csvString) {}`. If provided, will callback asynchronously. Only supported for compatibility reasons.
 
 #### Example `fields` option
 ``` javascript
@@ -145,16 +144,14 @@ car, price, color
 ### Example 2
 
 Similarly to [mongoexport](http://www.mongodb.org/display/DOCS/mongoexport) you can choose which fields to export.
-Note: this example uses the optional callback format.
 
 ```javascript
 var json2csv = require('json2csv');
 var fields = ['car', 'color'];
 
-json2csv({ data: myCars, fields: fields }, function(err, csv) {
-  if (err) console.log(err);
-  console.log(csv);
-});
+var csv = json2csv({ data: myCars, fields: fields });
+
+console.log(csv);
 ```
 
 Results in

lib/json2csv.js

@@ -32,38 +32,17 @@ var flatten = require('flat');
 /**
  * Main function that converts json to csv.
  *
- * @param {Json2CsvParams} params Function parameters containing data, fields,
- * delimiter (default is ','), header (default is true)
- * and default value (default is '')
- * @param {Function} [callback] Callback function
- *   if error, returning error in call back.
- *   if csv is created successfully, returning csv output to callback.
+ * @param {Json2CsvParams} params parameters containing data and
+ * and options to configure how that data is processed.
+ * @returns {String} The CSV formated data as a string
  */
-module.exports = function (params, callback) {
-  var hasCallback = typeof callback === 'function';
-
-  try {
-    checkParams(params);
-  } catch (err) {
-    if (hasCallback) {
-      return process.nextTick(function () {
-        callback(err);
-      });
-    } else {
-      throw err;
-    }
-  }
+module.exports = function (params) {
+  checkParams(params);
 
   var titles = createColumnTitles(params);
   var csv = createColumnContent(params, titles);
 
-  if (hasCallback) {
-    return process.nextTick(function () {
-      callback(null, csv);
-    });
-  } else {
-    return csv;
-  }
+  return csv;
 };