JSON to CSV Conversion: The Complete Developer's Guide

Input JSON:

[
  {
    "name": "John Doe",
    "age": 30,
    "email": "[email protected]",
    "department": "Engineering"
  },
  {
    "name": "Jane Smith",
    "age": 28,
    "email": "[email protected]",
    "department": "Marketing"
  },
  {
    "name": "Bob Johnson",
    "age": 35,
    "email": "[email protected]",
    "department": "Sales"
  }
]

Output CSV:

name,age,email,department
John Doe,30,[email protected],Engineering
Jane Smith,28,[email protected],Marketing
Bob Johnson,35,[email protected],Sales

Complex JSON with Nested Objects:

[
  {
    "name": "John Doe",
    "contact": {
      "email": "[email protected]",
      "phone": "+1-555-0123"
    },
    "address": {
      "street": "123 Main St",
      "city": "New York",
      "zipcode": "10001"
    },
    "skills": ["JavaScript", "Python", "SQL"]
  }
]

Flattened CSV Output:

name,contact.email,contact.phone,address.street,address.city,address.zipcode,skills
John Doe,[email protected],+1-555-0123,123 Main St,New York,10001,"JavaScript,Python,SQL"

const fs = require('fs');

function jsonToCsv(jsonArray) {
  if (!jsonArray.length) return '';
  
  // Get all unique keys
  const keys = [...new Set(jsonArray.flatMap(Object.keys))];
  
  // Create header
  const header = keys.join(',');
  
  // Create rows
  const rows = jsonArray.map(obj => 
    keys.map(key => {
      const value = obj[key] ?? '';
      // Handle strings with commas or quotes
      if (typeof value === 'string' && (value.includes(',') || value.includes('"'))) {
        return '"' + value.replace(/"/g, '""') + '"';
      }
      return value;
    }).join(',')
  );
  
  return [header, ...rows].join('\n');
}

// Usage
const jsonData = [
  { name: "John", age: 30, city: "New York" },
  { name: "Jane", age: 25, city: "Los Angeles" }
];

const csvOutput = jsonToCsv(jsonData);
fs.writeFileSync('output.csv', csvOutput, 'utf8');

import json
import pandas as pd
from pandas import json_normalize

def json_to_csv(json_data, output_file):
    """
    Convert JSON to CSV with nested object flattening
    """
    # Load JSON if it's a string
    if isinstance(json_data, str):
        data = json.loads(json_data)
    else:
        data = json_data
    
    # Normalize nested JSON
    df = json_normalize(data)
    
    # Save to CSV with UTF-8 encoding
    df.to_csv(output_file, index=False, encoding='utf-8-sig')
    
    return df

# Usage
json_data = [
    {
        "name": "John",
        "contact": {"email": "[email protected]", "phone": "555-0123"},
        "skills": ["Python", "JavaScript"]
    }
]

df = json_to_csv(json_data, 'output.csv')
print(df.head())