Go Small JSONPath

Small, feature limited JSONPath (+dialect) implementation.

✅ Features

• Query that returns a single value
• Safe query; returns zero value on failure
• Negative value index; index from the last element, e.g.. foo[-1].bar

🛑 Unsupported features

• Query that returns multiple values
• Conditional query
• Wildcard
• Descendant node query
• Aggregate functions
• Other functions

⭐ Dialect

Function

first

Returns the first item in the array.

$.foo.(first).bar

last

Returns the last item in the array.

$.foo.(last).bar

length

Returns the length of the array.

$.foo.(length)

🚀 Usage

package main

import (
	"fmt"
	"github.com/shellyln/go-small-jsonpath/jsonpath"
)

func main() {
    json, err := jsonpath.ReadString(`{"test":[{"abc":1},{"abc":10}]}`)
    if err != nil {
        fmt.Printf("ReadString: error = %v\n", err)
        return
    }

    path, err := jsonpath.Compile(`$.test[1].abc`)
    if err != nil {
        fmt.Printf("Compile: error = %v\n", err)
        return
    }

    v, err := path.Query(json) // returns nil, float64, string, []any, map[string]any
    if err != nil {
        fmt.Printf("Query: error = %v\n", err)
        return
    }
    fmt.Printf("Query: %v\n", v) // float64(10)

    vn := path.QueryAsNumberOrZero(json) // returns zero value on failure
    fmt.Printf("QueryAsNumberOrZero: %v\n", vn) // float64(10)

    vs := path.QueryAsStringOrZero(json) // returns zero value on failure
    fmt.Printf("QueryAsStringOrZero: %v\n", vs) // "" (zero value)
}

🪄 Query examples

Data:

{
    "foo": [11, 12, 13],
    "bar": "abcdefg",
    "baz": -9876,
    "qux": {
        "quux": null
    }
}

Queries:

> $.foo[0]
11

> $['foo'][1]
12

> $['foo'][3]
error (index out of range)

> $['foo'][-1]
13

> $["foo"].(length)
3

> $["foo"].(first)
11

> $["foo"].(last)
13

> $.bar
"abcdefg"

> $.bar.(length)
error (unsupported function operand)

> $.qux.quux
nil

> $['qux'].quux
nil

> $['qux']["quux"]
nil

> $.foo
map[string]any{...}

> $.qux
[]any{...}

⚖️ License

MIT
Copyright (c) 2023 Shellyl_N and Authors.