Changed up the parameters to include 'arr' the row data arr after some practical use

docs/docs.html

@@ -512,8 +512,9 @@ var csv = Papa.unparse({
 								<td>
 									A function to apply on each header. Requires <code>header</code> to be <code>true</code>. The function receives the header as its first argument and the index (the column number) as second. When used in conjunction with config.headerLines, the function receives a third and fourth parameter which are:
 									<ul>
-										<li>the existing header for that column based on previous lines iteration ('' if no previous lines)</li>
-										<li>the rowNumber (0 for the first line)</li>
+										<li><b>arr:</b> the string array of data for that row</li>
+										<li><b>acc:</b> the existing header for that column based on previous lines iteration ('' if no previous lines)</li>
+										<li><b>j:</b> the rowNumber (0 for the first line)</li>
 									</ul>
 								</td>
 							</tr>

papaparse.js

@@ -1181,10 +1181,10 @@ License: MIT
 				return;
 
 			var headerLines = _config.headerLines || 1;
-			function addHeader(j, header, i)
+			function addHeader(j, header, i, arr)
 			{
 				if (isFunction(_config.transformHeader))
-					header = _config.transformHeader(header, i, _fields[i] || '', j);
+					header = _config.transformHeader(header, i, arr, _fields[i] || '', j);
 
 				_fields[i] = header;
 			}

tests/test-cases.js

@@ -770,7 +770,7 @@ var PARSE_TESTS = [
 	{
 		description: "Header row is generated from multiple rows when transformheader function is provided and config.headerLines is set",
 		input: "A,B,C\r\nD,E,F\r\nG,H,I\r\nadg,beh,cfi",
-		config: { header: true, transformHeader: function(header, i, acc, j) { return acc + (j % 2 ? header.toLowerCase() : header); }, headerLines: 3 },
+		config: { header: true, transformHeader: function(header, i, arr, acc, j) { return acc + (j % 2 ? header.toLowerCase() : header); }, headerLines: 3 },
 		expected: {
 			data: [{"AdG": "adg", "BeH": "beh", "CfI": "cfi"}],
 			errors: []