orderedmap

A generic ordered map implementation in Go that preserves insertion order and supports JSON serialization/deserialization.

Installation

go get github.com/kazamori/orderedmap

Features

• Generic type support with OrderedMap[K, V]
• Preserves insertion order of keys
• JSON marshaling/unmarshaling with order preservation
• O(1) key lookup

Quick Start

package main

import (
    "encoding/json"
    "fmt"

    "github.com/kazamori/orderedmap"
)

func main() {
    // Create a new ordered map
    m := orderedmap.New[string, any]()
    m.Set("name", "Alice")
    m.Set("age", 30)
    m.Set("active", true)

    // Iterate in insertion order
    for _, p := range m.Pairs() {
        fmt.Printf("%s: %v\n", p.Key, p.Value)
    }

    // Get a value
    if val, ok := m.Get("name"); ok {
        fmt.Println("Name:", val)
    }

    // Serialize to JSON (preserves order)
    data, _ := json.Marshal(m)
    fmt.Println(string(data))
    // Output: {"name":"Alice","age":30,"active":true}
}

JSON Unmarshaling

Parse JSON while preserving the original key order:

jsonData := []byte(`{"z":"last","a":"first","m":"middle"}`)
m := orderedmap.New[string, any]()
json.Unmarshal(jsonData, m)

for _, p := range m.Pairs() {
    fmt.Printf("%s: %v\n", p.Key, p.Value)
}
// Output:
// z: last
// a: first
// m: middle

API Reference

Function/Method	Description
New[K, V]()	Create a new empty ordered map
WithCapacity[K, V](size)	Create with pre-allocated capacity
NewFromMap[M, K, V](m)	Create from a standard Go map
Set(key, value)	Add or update a key-value pair
Get(key)	Retrieve a value by key
Pairs()	Get all pairs in insertion order
String()	JSON string representation
ToMap[M, K, V](om)	Convert to standard Go map

Examples

See example_test.go for more usage examples.

CLI Tool

A CLI tool is included for testing JSON round-trip serialization:

make build
./bin/cli -data '{"s":"test","i":3,"a":[{"f":3.14},{"b":true}]}'

Output:

{
  "s": "test",
  "i": 3,
  "a": [
    {
      "f": 3.14
    },
    {
      "b": true
    }
  ]
}