Pretty JSON Formatter

Overview

Pretty is a high-performance Go package for formatting JSON with flexible pretty-printing capabilities, featuring customizable indentation and depth control.

Key Features

• 🚀 High Performance - Optimized with fastjson and bytebufferpool for minimal memory allocation
• 🎨 Flexible Formatting - Configurable indentation styles and depth control
• ⚙️ Multiple Input Types - Supports []byte, string, *fastjson.Value, and any JSON-serializable Go value
• 📏 Depth Control - Configurable max/min expansion depth
• 🔄 Dual Output Modes - Pretty-printed (Format) and compact (Ugly) output

Installing

go get -u github.com/zc310/pretty

Usage Examples

Basic Usage

{
  "firstName": "John",
  "lastName": "Smith",
  "isAlive": true,
  "age": 27,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021-3100"
  },
  "phoneNumbers": [
    {
      "type": "home",
      "number": "212 555-1234"
    },
    {
      "type": "office",
      "number": "646 555-4567"
    }
  ],
  "children": [
    "Catherine",
    "Thomas",
    "Trevor"
  ],
  "spouse": null
}

The following code:

result = pretty.Format(example)

Will format the json to:

{
  "firstName":"John",
  "lastName":"Smith",
  "isAlive":true,
  "age":27,
  "address":{"streetAddress":"21 2nd Street","city":"New York","state":"NY","postalCode":"10021-3100"},
  "phoneNumbers":[{"type":"home","number":"212 555-1234"},{"type":"office","number":"646 555-4567"}],
  "children":["Catherine","Thomas","Trevor"],
  "spouse":null
}

package main

import (
	"fmt"
	"github.com/zc310/pretty"
)

func main() {
	jsonStr := `{"name":"John","age":30,"address":{"city":"New York","zip":"10001"}}`
	
	// Default formatting
	fmt.Println(string(pretty.Format(jsonStr)))
	
	// Compact output
	fmt.Println(string(pretty.Ugly(jsonStr)))
	
	// Custom options
	opts := &pretty.Options{
		Indent:   "    ",  // 4-space indent
		MaxDepth: 2,      // Max expansion depth
	}
	fmt.Println(string(pretty.FormatOptions(jsonStr, opts)))
}

Advanced Usage

// Format directly from Go values
data := map[string]interface{}{
	"name": "Alice",
	"skills": []string{"Go", "JavaScript", "Python"},
}
fmt.Println(string(pretty.Format(data)))

// Handle fastjson.Value
val, _ := fastjson.Parse(`{"key":"value"}`)
fmt.Println(string(pretty.Format(val)))

API Reference

Options Struct

type Options struct {
	Indent   string // Indentation string (default: two spaces)
	MaxDepth int    // Maximum expansion depth (0 = unlimited)
	MinDepth int    // Minimum expansion depth (0 = unlimited)
}

Core Functions

• Format(o any) []byte - Format with default options
• Ugly(o any) []byte - Compact output (no formatting)
• FormatOptions(o any, opts *Options) []byte - Format with custom options

Performance Optimization

1. Buffer Pool Management - Uses bytebufferpool to reduce memory allocations
2. Zero-Copy Processing - Directly operates on raw JSON bytes
3. Optimized Depth Calculation - Efficient nested depth computation
4. Minimal String Operations - Avoids unnecessary string conversions and concatenations