How to Convert CSV to JSON

// Basic CSV to JSON
function csvToJson(csv, options = {}) {
  const { delimiter = ',', typeDetection = false } = options;
  const lines = csv.trim().split('\n');
  const headers = parseCsvLine(lines[0], delimiter);
  
  return lines.slice(1)
    .filter(line => line.trim())
    .map(line => {
      const values = parseCsvLine(line, delimiter);
      return headers.reduce((obj, header, i) => {
        let value = values[i] || '';
        if (typeDetection) {
          value = parseValue(value);
        }
        obj[header.trim()] = value;
        return obj;
      }, {});
    });
}

// Parse CSV line handling quotes
function parseCsvLine(line, delimiter = ',') {
  const result = [];
  let current = '';
  let inQuotes = false;
  
  for (let i = 0; i < line.length; i++) {
    const char = line[i];
    if (char === '"') {
      if (inQuotes && line[i + 1] === '"') {
        current += '"';
        i++;
      } else {
        inQuotes = !inQuotes;
      }
    } else if (char === delimiter && !inQuotes) {
      result.push(current);
      current = '';
    } else {
      current += char;
    }
  }
  result.push(current);
  return result;
}

// Detect and convert types
function parseValue(value) {
  if (value === '') return null;
  if (value.toLowerCase() === 'true') return true;
  if (value.toLowerCase() === 'false') return false;
  if (value.toLowerCase() === 'null') return null;
  if (!isNaN(value) && value.trim() !== '') return Number(value);
  return value;
}

// Usage
const csv = `name,age,active
John,30,true
Jane,25,false`;

console.log(JSON.stringify(csvToJson(csv, { typeDetection: true }), null, 2));

import csv
import json

# Using csv module
def csv_to_json(csv_string, type_detection=False):
    lines = csv_string.strip().split('\n')
    reader = csv.DictReader(lines)
    result = []
    
    for row in reader:
        if type_detection:
            row = {k: parse_value(v) for k, v in row.items()}
        result.append(row)
    
    return result

def parse_value(value):
    if value == '':
        return None
    if value.lower() == 'true':
        return True
    if value.lower() == 'false':
        return False
    try:
        if '.' in value:
            return float(value)
        return int(value)
    except ValueError:
        return value

# Using pandas (recommended for large files)
import pandas as pd

# CSV file to JSON
df = pd.read_csv("data.csv")
json_data = df.to_json(orient='records', indent=2)
print(json_data)

# Or save to file
df.to_json("output.json", orient='records', indent=2)

# With type inference (pandas does this automatically)
df = pd.read_csv("data.csv", dtype={
    'id': int,
    'price': float,
    'active': bool
})

# CSV string to JSON
from io import StringIO
csv_data = """name,age,active
John,30,true
Jane,25,false"""

df = pd.read_csv(StringIO(csv_data))
print(df.to_json(orient='records'))

# Using miller (mlr)
# Install: brew install miller
mlr --csv --ojson cat data.csv > output.json

# Using jq with @csv (reverse)
# Note: jq reads JSON, not CSV directly

# Using csvkit
# pip install csvkit
csvjson data.csv > output.json

# With indentation
csvjson data.csv | python -m json.tool > output.json

# Using Node.js csvtojson
# npm install -g csvtojson
csvtojson data.csv > output.json

# Python one-liner
python -c "import csv,json,sys; print(json.dumps(list(csv.DictReader(sys.stdin)), indent=2))" < data.csv > output.json

# Convert multiple files
for f in *.csv; do
  csvjson "$f" > "${f%.csv}.json"
done

# With specific delimiter
mlr --csv --fs ';' --ojson cat semicolon-data.csv > output.json

// Different delimiters
function detectDelimiter(line) {
  const delimiters = [',', ';', '\t', '|'];
  return delimiters.reduce((best, d) => {
    const count = line.split(d).length;
    return count > best.count ? { delimiter: d, count } : best;
  }, { delimiter: ',', count: 0 }).delimiter;
}

// Handle BOM (Byte Order Mark)
function removeBOM(text) {
  return text.replace(/^\uFEFF/, '');
}

// Normalize line endings
function normalizeLineEndings(text) {
  return text.replace(/\r\n/g, '\n').replace(/\r/g, '\n');
}

// Handle inconsistent columns
function csvToJsonWithMissingValues(csv) {
  const lines = csv.trim().split('\n');
  const headers = parseCsvLine(lines[0]);
  
  return lines.slice(1).map(line => {
    const values = parseCsvLine(line);
    return headers.reduce((obj, header, i) => {
      // Use null for missing values
      obj[header] = values[i] !== undefined ? values[i] : null;
      return obj;
    }, {});
  });
}

// Handle multiline values (quoted)
const csvWithMultiline = `name,description
John,"This is a
multiline description"
Jane,"Single line"`;

// The parseCsvLine function handles this with quote tracking

// Skip empty rows
function csvToJsonSkipEmpty(csv) {
  const lines = csv.trim().split('\n')
    .filter(line => line.trim() && !line.match(/^,*$/));
  // ... rest of parsing
}

// Nested JSON from dot notation headers
const flatCsv = "user.name,user.email,orders\nJohn,john@example.com,5";
// Can be transformed to nested objects if needed