TemperTemper

Parse CSV with Quotes

Parse CSV handling quoted fields containing commas and escaped quotes. Follows RFC 4180 standard for proper CSV parsing.

Code

Utilities
const rows = [];
let row = [], field = '', inQuotes = false;
for (let i = 0; i < csv.length; i++) {
  const c = csv[i], next = csv[i + 1];
  if (inQuotes) {
    if (c === '"' && next === '"') { field += '"'; i++; }
    else if (c === '"') inQuotes = false;
    else field += c;
  } else {
    if (c === '"') inQuotes = true;
    else if (c === ',') { row.push(field); field = ''; }
    else if (c === '\n' || (c === '\r' && next === '\n')) {
      row.push(field); rows.push(row); row = []; field = '';
      if (c === '\r') i++;
    } else field += c;
  }
}
if (field || row.length) { row.push(field); rows.push(row); }
return rows;

Parameters

CSV content.

Browser·fetch() may be limited by CORS

Why Not Just Split on Commas?

Simple splitting breaks on quoted content:

// WRONG: Splits inside quotes
"hello,world".split(',')           // ["hello", "world"] ✓
'"hello,world"'.split(',')         // ['"hello', 'world"'] ✗

// Need proper parsing:
parseCSV('"hello,world"')          // [["hello,world"]] ✓

RFC 4180 Rules

This parser follows the CSV standard:

RuleExample
Fields separated by commasa,b,c
Rows separated by newlinesa,b\nc,d
Quotes wrap fields with special chars"has,comma"
Escaped quotes are doubled"say ""hello""" → say "hello"
Newlines allowed in quoted fields"line1\nline2"

Parsing Examples

Input:
name,description,price
"Widget","A small, handy tool",9.99
"Gadget","Say ""hello""",19.99

Output:
[
  ["name", "description", "price"],
  ["Widget", "A small, handy tool", "9.99"],
  ["Gadget", "Say \"hello\"", "19.99"]
]

Common Edge Cases

// Empty fields
"a,,c"           → ["a", "", "c"]

// Quoted empty string
'a,"",c'         → ["a", "", "c"]

// Only whitespace (preserved)
"a, b ,c"        → ["a", " b ", "c"]

// Newline in quoted field
'"line1\nline2"' → ["line1\nline2"]

Converting to Objects

To get objects with headers as keys:

const [headers, ...data] = rows;
const objects = data.map(row =>
  Object.fromEntries(headers.map((h, i) => [h, row[i]]))
);
// [{name: "Widget", description: "A small, handy tool", price: "9.99"}, ...]

When to Use a Library

For production CSV handling, consider:

  • Papa Parse — Fast, streaming, auto-detect delimiters
  • csv-parse — Node.js streams, extensive options
  • D3-dsv — Part of D3.js, handles TSV too

This snippet is perfect for quick parsing of known-good CSV data.

More JavaScript Snippets

Capitalize First Letter

Capitalize the first letter of a string while keeping the rest unchanged.

Center String

Center a string within a given width by padding with spaces.

Check if Palindrome

Check if a string is a palindrome by comparing characters from both ends.

Compare Strings (Case Insensitive)

Compare two strings ignoring case differences.

Convert to Camel Case

Convert a string to camelCase format with lowercase first letter.

Convert to Kebab Case

Convert a string to kebab-case format.