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tessl/npm-prettyjson

Package for formatting JSON data in a coloured YAML-style, perfect for CLI output

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prettyjson

prettyjson is a Node.js package that transforms JSON data into a colorized, YAML-style output format, perfect for command-line interfaces and console applications. It provides both programmatic API access and a command-line interface with extensive customization options for colors, indentation, and formatting styles.

Package Information

  • Package Name: prettyjson
  • Package Type: npm
  • Language: JavaScript
  • Installation: npm install prettyjson (or npm install -g prettyjson for CLI)

Core Imports

const prettyjson = require('prettyjson');

ESM import (if supported):

import prettyjson from 'prettyjson';

Basic Usage

const prettyjson = require('prettyjson');

const data = {
  username: 'alice',
  projects: ['web-app', 'mobile-app'],
  settings: {
    theme: 'dark',
    notifications: true
  }
};

// Basic rendering
console.log(prettyjson.render(data));

// With custom options
console.log(prettyjson.render(data, {
  keysColor: 'rainbow',
  dashColor: 'magenta',
  stringColor: 'white',
  noColor: false
}));

// Parse and render JSON string
const jsonString = '{"name": "Bob", "age": 30}';
console.log(prettyjson.renderString(jsonString));

// Access version information
console.log('Using prettyjson version:', prettyjson.version);

Architecture

prettyjson is built around a simple, focused architecture:

  • Core Rendering Engine: Recursive data structure traversal with type-specific formatting
  • Color System: Integration with colors.js for terminal color output
  • CLI Interface: Complete command-line tool with argument parsing and multiple input methods
  • Configuration System: Extensive options for customizing output appearance and behavior

Capabilities

Data Rendering

Core function for converting JavaScript data structures into formatted, colorized YAML-style output.

/**
 * Renders data as formatted, colorized YAML-style output
 * @param data - Data to render (any type)
 * @param options - Configuration options (optional, object)
 * @param indentation - Base indentation level (optional, number, default: 0)
 * @returns string - Formatted string output
 */
function render(data: any, options?: Options, indentation?: number): string;

String Parsing and Rendering

Function for parsing JSON strings and rendering them with formatting.

/**
 * Parses JSON string and renders it with formatting
 * @param data - JSON string to parse and render
 * @param options - Configuration options (optional, object)  
 * @param indentation - Base indentation level (optional, number, default: 0)
 * @returns string - Formatted string output or error message if invalid JSON
 */
function renderString(data: string, options?: Options, indentation?: number): string;

Version Information

Access to the package version.

/**
 * Package version string accessed from the module
 */
const prettyjson = require('prettyjson');
const version: string = prettyjson.version;

Command Line Interface

Complete CLI tool for processing JSON files and streams.

Usage:

# Render a JSON file
prettyjson package.json

# Process stdin
curl https://api.github.com/users/alice | prettyjson

# Interactive mode (no arguments)
prettyjson

CLI Options:

--keys COLOR           # Set color for object keys
--dash COLOR           # Set color for array dashes  
--string COLOR         # Set color for strings
--multiline_string COLOR # Set color for multiline strings
--number COLOR         # Set color for numbers
--indent NUMBER        # Set indentation spaces
--nocolor             # Disable colors
--noalign             # Disable value alignment
--escape              # Escape conflicting characters
--inline-arrays       # Render simple arrays inline

Environment Variables:

  • PRETTYJSON_KEYS - Default keys color
  • PRETTYJSON_DASH - Default dash color
  • PRETTYJSON_STRING - Default string color
  • PRETTYJSON_MULTILINE_STRING - Default multiline string color
  • PRETTYJSON_NUMBER - Default number color
  • PRETTYJSON_NUMBER_POSITIVE - Default positive number color
  • PRETTYJSON_NUMBER_NEGATIVE - Default negative number color
  • PRETTYJSON_INDENT - Default indentation
  • PRETTYJSON_NOCOLOR - Disable colors
  • PRETTYJSON_NOALIGN - Disable alignment
  • PRETTYJSON_ESCAPE - Enable escaping
  • PRETTYJSON_INLINE_ARRAYS - Enable inline arrays

Configuration Options

interface Options {
  /** Message displayed for empty arrays (default: '(empty array)') */
  emptyArrayMsg?: string;
  
  /** Color for object keys using colors.js syntax (default: 'green') */
  keysColor?: string;
  
  /** Color for array item dashes (default: 'green') */
  dashColor?: string;
  
  /** Color for all numbers (default: 'blue') */
  numberColor?: string;
  
  /** Color for positive numbers (default: uses numberColor) */
  positiveNumberColor?: string;
  
  /** Color for negative numbers (default: uses numberColor) */
  negativeNumberColor?: string;
  
  /** Color for strings (default: null - no coloring) */
  stringColor?: string | null;
  
  /** Color for multiline strings (default: null - no coloring) */
  multilineStringColor?: string | null;
  
  /** Indentation for nested objects in spaces (default: 2) */
  defaultIndentation?: number;
  
  /** Disable all coloring (default: false) */
  noColor?: boolean;
  
  /** Disable value alignment (default: false) */
  noAlign?: boolean;
  
  /** Escape conflicting characters with JSON.stringify (default: false) */
  escape?: boolean;
  
  /** Render undefined values instead of ignoring them (default: false) */
  renderUndefined?: boolean;
  
  /** Render simple arrays inline instead of multi-line (default: false) */
  inlineArrays?: boolean;
}

Data Type Support

prettyjson handles all JavaScript data types:

  • Primitives: strings, numbers, booleans, null, undefined
  • Objects: Plain objects with proper key formatting and indentation
  • Arrays: Multi-line with dash prefixes, or inline mode for simple arrays
  • Functions: Rendered as "function() {}"
  • Dates: Rendered using default toString() representation
  • Errors: Special handling to display message and stack trace
  • Multiline Strings: Triple-quote formatting with proper indentation

Color System

Colors are specified using colors.js syntax:

Standard Colors: black, red, green, yellow, blue, magenta, cyan, white, gray, grey

Bright Colors: brightRed, brightGreen, brightYellow, brightBlue, brightMagenta, brightCyan, brightWhite

Special Effects: rainbow, zebra, america, trap, random

Styles: bold, dim, italic, underline, inverse, hidden, strikethrough

Error Handling

  • Invalid JSON: renderString() returns "Error: Not valid JSON!" in red text when JSON parsing fails
  • Empty String Input: renderString() with empty string returns empty string
  • Non-string Input: renderString() with non-string input returns empty string
  • File Not Found: CLI displays error message in red and exits with code 1
  • Undefined Values: Ignored by default unless renderUndefined: true option is set
  • Function Values: Rendered as "function() {}" string representation
  • Circular References: May cause stack overflow (not explicitly handled)
  • Error Objects: Special handling to display message and stack trace properties

docs

index.md

tile.json