csv-parser.js

function parseComplexCSV(input, separator, quote) {
  separator = separator || ',';
  quote = quote || '"';

  return input
    .replace(new RegExp('\\'+quote+'\\'+quote,'g'), 'doubleQuoteFlag')
    .split(quote)
    .map(function(val, index) {
      return index%2 ? 
        val.replace(new RegExp('doubleQuoteFlag','g'), quote) : 
        val.replace(new RegExp('\n','g'),'splitByMeFirst')
           .replace(new RegExp('\\' + separator,'g'),'splitByMeSecond')
           .replace(new RegExp('doubleQuoteFlag','g'), '');
    })
    .join('')
    .split('splitByMeFirst')
    .map(function(val) {
      return val.split('splitByMeSecond');
    });
}

Test cases:

describe("CSV Parser Test Cases", function() {
  it("should handle simple inputs", function() {
    var input = "1,2,3\n4,5,6";
    var output = [['1','2','3'],['4','5','6']];
    Test.assertSimilar(parseComplexCSV(input), output);
  });
  it("should handle quoted fields", function() {
    var input = "1,\"two was here\",3\n4,5,6";
    var output = [['1','two was here','3'],['4','5','6']];
    Test.assertSimilar(parseComplexCSV(input), output);
  });
  it("should handle leading and trailing spaces in quoted fields", function() {
    var input = "1,\" two \",3\n4,5,6";
    var output = [['1',' two ','3'],['4','5','6']];
    Test.assertSimilar(parseComplexCSV(input), output);
  });
  it("should handle separators in quoted fields", function() {
    var input = "1,\"hello, world\",3\n4,5,6";
    var output = [['1','hello, world','3'],['4','5','6']];
    Test.assertSimilar(parseComplexCSV(input), output);
  });
  it("should handle alternate separators", function() {
    var input = "1\t2\t3\n4\t5\t6";
    var output = [['1','2','3'],['4','5','6']];
    Test.assertSimilar(parseComplexCSV(input, '\t'), output);
  });
  it("should handle empty rows", function() {
    var input = "1,\"two was here\",3\n\n4,5,6";
    var output = [['1','2','3'],[''],['4','5','6']];
    Test.assertSimilar(parseComplexCSV(input), output);
  });
});