Added support for renaming duplicate headers

papaparse.js

@@ -1457,6 +1457,34 @@ License: MIT
 			if (!input)
 				return returnable();
 
+			// Rename headers if there are duplicates
+			if (config.header)
+			{
+				let firstLine = input.split(newline)[0]
+				let separator = '_';
+				let headers = firstLine.split(delim) 
+				let header_map = []; 
+				let header_count = {};
+
+				for (var i in headers){
+					if (!header_map.includes(headers[i])){
+						header_map.push(headers[i])
+					}
+					else{
+						if (!(headers[i] in header_count)){
+							header_count[headers[i]] = 1
+						}
+						else{
+							header_count[headers[i]] +=1
+						}
+						header_map.push(headers[i]+separator+header_count[headers[i]])
+					}
+				}
+				var edited_input = input.split(newline)
+				edited_input[0] = header_map.join(delim)
+				input = edited_input.join(newline)
+			}
+
 			if (fastMode || (fastMode !== false && input.indexOf(quoteChar) === -1))
 			{
 				var rows = input.split(newline);

tests/test-cases.js

@@ -585,6 +585,15 @@ var CORE_PARSER_TESTS = [
 			data: [['a', 'b', 'c'], ['']],
 			errors: []
 		}
+	},
+	{
+		description: "Duplicate header names",
+		input: 'A,A,A,A\n1,2,3,4',
+		config: { header: true },
+		expected: {
+			data: [['A', 'A_1', 'A_2', 'A_3'], ['1', '2', '3', '4']],
+			errors: []
+		}
 	}
 ];