JSON Array to CSV Conversion

Converting JSON to CSV

Turning a JSON array of objects into CSV is the reverse of the typical CSV-to-JSON workflow. The process requires extracting a consistent set of column headers from potentially varied objects.

Input JSON

[
  { "id": 1, "product": "Widget", "price": 9.99, "inStock": true },
  { "id": 2, "product": "Gadget", "price": 24.50, "inStock": false },
  { "id": 3, "product": "Doohickey", "price": 4.75, "inStock": true }
]

Output CSV

id,product,price,inStock
1,Widget,9.99,true
2,Gadget,24.50,false
3,Doohickey,4.75,true

Step-by-step process

1. Collect all unique keys. Iterate through every object in the array and build a union of all property names. This becomes the header row.
2. Write the header. Join the keys with commas (or your chosen delimiter) and output as the first line.
3. Serialize each object. For every object, look up each header key and output the corresponding value. If a key is missing from an object, output an empty string.
4. Escape special characters. If a value contains a comma, double-quote, or newline, wrap it in double quotes. Any internal double quotes must be doubled ("").

Handling type differences

JSON supports booleans, numbers, null, nested objects, and arrays. CSV is plain text. Common strategies:

JSON type	CSV representation
string	As-is (quote if contains delimiter)
number	Numeric string
boolean	"true" or "false"
null	Empty string
object/array	JSON-stringified or flattened

When objects have nested structures, you need a flattening strategy (see Flattening Nested JSON for CSV). For flat JSON arrays, the conversion is straightforward and lossless for primitive types.