jsonpath

package main

import (
	"fmt"

	"github.com/theory/jsonpath"
)

func main() {
	// Load some JSON.
	menu := map[string]any{
		"apps": map[string]any{
			"guacamole": 19.99,
			"salsa":     5.99,
		},
	}

	// Parse a JSONPath and select from the input.
	p := jsonpath.MustParse(`$.apps["salsa", "guacamole"]`)
	nodes := p.SelectLocated(menu)

	// Show the nodes.
	fmt.Println("Nodes:")
	for n := range nodes.Nodes() {
		fmt.Printf("  %v\n", n)
	}

	// Show the paths.
	fmt.Println("\nPaths:")
	for p := range nodes.Paths() {
		fmt.Printf("  %v\n", p)
	}

}

Output:
Nodes:
  5.99
  19.99

Paths:
  $['apps']['salsa']
  $['apps']['guacamole']

Use the Parser to parse a collection of paths.

package main

import (
	"encoding/json"
	"fmt"
	"log"

	"github.com/theory/jsonpath"
)

func main() {
	// Create a new parser using the default function registry.
	parser := jsonpath.NewParser()

	// Parse a list of paths.
	strings := []string{
		"$.store.book[*].author",
		"$..author",
		"$.store..color",
		"$..book[2].author",
		"$..book[2].publisher",
		"$..book[?@.isbn].title",
		"$..book[?@.price<10].title",
	}
	paths := make([]*jsonpath.Path, 0, len(strings))
	for _, path := range strings {
		p, err := parser.Parse(path)
		if err != nil {
			log.Fatal(err)
		}
		paths = append(paths, p)
	}

	// Later, use the paths to select from JSON inputs.
	store := bookstore()
	for _, p := range paths {
		items := p.Select(store)
		array, err := json.Marshal(items)
		if err != nil {
			log.Fatal(err)
		}

		fmt.Printf("%s\n", array)
	}
}

// bookstore returns an unmarshaled JSON object.
func bookstore() any {
	src := []byte(`{
	  "store": {
	    "book": [
	    {
	      "category": "reference",
	      "author": "Nigel Rees",
	      "title": "Sayings of the Century",
	      "price": 8.95
	    },
	    {
	      "category": "fiction",
	      "author": "Evelyn Waugh",
	      "title": "Sword of Honour",
	      "price": 12.99
	    },
	    {
	      "category": "fiction",
	      "author": "Herman Melville",
	      "title": "Moby Dick",
	      "isbn": "0-553-21311-3",
	      "price": 8.99
	    },
	    {
	      "category": "fiction",
	      "author": "J. R. R. Tolkien",
	      "title": "The Lord of the Rings",
	      "isbn": "0-395-19395-8",
	      "price": 22.99
	    }
	    ],
	    "bicycle": {
	    "color": "red",
	    "price": 399
	    }
	  }
	}`)

	var value any
	if err := json.Unmarshal(src, &value); err != nil {
		log.Fatal(err)
	}
	return value
}

Output:
["Nigel Rees","Evelyn Waugh","Herman Melville","J. R. R. Tolkien"]
["Nigel Rees","Evelyn Waugh","Herman Melville","J. R. R. Tolkien"]
["red"]
["Herman Melville"]
[]
["Moby Dick","The Lord of the Rings"]
["Sayings of the Century","Moby Dick"]