Flatten Nested JSON to CSV: Dot Notation and Arrays
Flatten deeply nested JSON into flat CSV rows. Understand dot-notation key expansion, array exploding, and when flattening loses information.
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Tags: data, json, csv
Flatten Nested JSON to CSV: Dot Notation, Arrays, and Deep Objects Flattening nested JSON to CSV is the step that breaks most converters. The naive approach — iterate keys, write values — falls apart the moment you hit an object as a value or an array mid-record. This post covers the algorithms you actually need: dot-notation for nested objects, row-expansion versus joining for arrays, and strategies for inconsistent depth across records. --- The Core Problem CSV is a two-dimensional format: rows and columns. JSON is N-dimensional: objects nest inside objects, arrays contain objects that contain arrays. Flattening is the process of collapsing those dimensions into two. Given this input: The expected flat output (dot-notation, arrays joined): Two decisions were made here: Nested objects →…
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