json-stringify-compact

JSON serialization with per-path decimal precision control.

stringifyCompact is a drop-in alternative to JSON.stringify that lets you pin specific numeric fields to a fixed number of decimal places using glob-style path patterns — without touching the rest of your data.

Features

• Pin numeric fields to exact decimal places via dot-notation path patterns
• Glob-style wildcards: * (single segment), [*] (array index), ** (any depth)
• Later rules win — compose coarse defaults with precise overrides
• Compact or pretty-printed output (space option, same as JSON.stringify)
• Zero dependencies, pure TypeScript

Installation

# npm
npm install @webstory/json-stringify-compact

# pnpm
pnpm add @webstory/json-stringify-compact

# bun
bun add @webstory/json-stringify-compact

Usage

import { stringifyCompact } from '@webstory/json-stringify-compact';

Basic example

const data = {
  name: 'sensor-A',
  reading: 1.23456789,
};

stringifyCompact(data);
// → '{"name":"sensor-A","reading":1.23456789}'

stringifyCompact(data, { defaultDecimals: 2 });
// → '{"name":"sensor-A","reading":1.23}'

Path rules

const data = {
  metrics: { cpu: 0.987654, mem: 0.512345 },
  version: 1.0,
};

stringifyCompact(data, {
  rules: [
    { path: 'metrics.*', decimals: 2 },
  ],
});
// → '{"metrics":{"cpu":0.99,"mem":0.51},"version":1}'

Array paths

const data = {
  readings: [1.23456, 2.34567, 3.45678],
};

stringifyCompact(data, {
  rules: [{ path: 'readings[*]', decimals: 1 }],
});
// → '{"readings":[1.2,2.3,3.5]}'

Deep wildcard (**)

const data = {
  a: { b: { c: { value: 1.23456 } } },
};

stringifyCompact(data, {
  rules: [{ path: '**.value', decimals: 2 }],
});
// → '{"a":{"b":{"c":{"value":1.23}}}}'

Rule precedence

Rules are evaluated in order, with later rules taking precedence over earlier ones.

stringifyCompact(data, {
  defaultDecimals: 4,
  rules: [
    { path: '**',           decimals: 4 },  // broad default
    { path: 'metrics.*',    decimals: 2 },  // more specific — wins
  ],
});

Pretty-printed output

stringifyCompact({ a: 1.5, b: [2.5, 3.5] }, {
  defaultDecimals: 1,
  space: 2,
});
// →
// {
//   "a": 1.5,
//   "b": [
//     2.5,
//     3.5
//   ]
// }

API

stringifyCompact(data, options?)

| Parameter | Type | Description | |-----------|------|-------------| | data | unknown | Any JSON-serializable value | | options | StringifyOptions | Optional formatting options |

Returns: string — the JSON-serialized output.

StringifyOptions

| Option | Type | Default | Description | |--------|------|---------|-------------| | defaultDecimals | number | undefined | Decimal precision for all numbers not matched by a rule | | rules | FormatRule[] | [] | Per-path decimal rules; later entries override earlier ones | | space | number | 0 | Indentation size in spaces (0 = compact, 2/4 = pretty) |

FormatRule

| Field | Type | Description | |-------|------|-------------| | path | string | Dot-notation path pattern (supports *, [*], **) | | decimals | number | Number of decimal places to apply via toFixed() |

Path pattern syntax

| Pattern | Matches | |---------|---------| | foo | Exactly the key foo at the root | | foo.bar | Nested key bar inside foo | | foo.* | Any direct child of foo | | foo[*] | Any element of the array foo | | **.value | Any key named value at any depth | | ** | Every node at any depth |

Development

# Install dependencies
npm install

# Run tests
npm test

# Run tests in watch mode
npm run test:watch

# Run tests with coverage
npm run test:coverage

# Build for publishing
npm run build

# Type-check without emitting
npm run typecheck

License

MIT — Hoya Kim