formatJson

Pretty-print JSON. Accepts an object, or a JSON string to reformat.

API

formatJson(value, onError?, indent?)

Parameter	Description	Type	Default
value	Object, or a JSON string (single quotes are tolerated)	string | object	Required
onError	Called with the parse/serialize error	(e: Error) => void	no-op
indent	Spaces per level	number	4

Returns the formatted string, or '' when the input cannot be parsed.

Example

import { formatJson } from 'ranuts';

formatJson({ a: 1, b: [2, 3] });
formatJson("{'a': 1}"); // single quotes tolerated
formatJson({ a: 1 }, undefined, 2); // 2-space indent
formatJson('nope', (e) => console.warn(e)); // '' and the error handed to the callback

Notes

1. A string input is re-parsed, not echoed. That validates it and normalizes the layout rather than trusting whatever spacing the caller had.
2. Errors are reported, never thrown — invalid JSON, circular structures and values JSON.stringify cannot represent all return '' and invoke onError.

Rewritten in 0.3

This was a ~90-line hand-rolled formatter that rebuilt the layout by regex-injecting newlines around every brace, bracket and comma, then tried to undo the damage inside string literals by counting quotes per line. It mis-handled escaped quotes and treated a brace or comma inside a string value as structure, so { css: 'a { color: red, }' } came out corrupted. It is now JSON.stringify with lenient parsing in front — correct, and far faster. Output spacing matches JSON.stringify rather than the old bespoke layout.