@amida-tech/jsonave

jsonave

A JSONPath Implementation

This library provides an implementation of JSONPath. Originally it was based on this implementation and added support for functions. Current version however is a complete rewrite and code is structured so that no performance penalties are paid when parent and path functionalities are not used. Original API and options are still supported.

Another implementation of JSONPath is jsonpath. jsonpath does not include the additional functionality to the original JSONPath such as functions and parent that this library provides. However it does use a fully defined BNF parser based on Jison. This library uses a manually implemented parser. No performance comparison to jsonpath has been made either for the parsers or the actual JSONPath engine.

In addition to functionality described here, this library implements ability to add functions as part of JSONPath. The example below illustrates the additional functionality. Some options functionality are also modified as follows

• wrap - Whether or not to wrap the results in an array. If wrap is set to true, the result will always be an array which can be empty. If wrap is set to false, and no results are found, null will be returned (as opposed to an empty array). If wrap is set to false and a single result is found, that result will be the only item returned. If wrap is not specified, it is set to true if branching elements (.., *, : (range), , (multiple properties)) are used and it will be set to false otherwise. An array will still be returned if multiple results are found, however.
• emptyValue - This specifies what to return if no results are found. If wrap is specified this defaults to [] and if it is not specified it defaults to null.

Quick up and running guide

Prerequisites

• Node.js (v14.19+) and NPM
• Grunt.js

# Install dependencies
npm i

# Install grunt
npm i -g grunt

# Test
grunt

Usage

instance(inputExpr, opts)

Returns a JSONPath evaluator. You can define functions for JSONPath expressions in opts.sandbox

var example = {
    "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": 19.95
        }
    }
};

var options = {
    sandbox: {
        round: function (obj) {
            return Math.round(obj);
        }
    }
};

var jp = jsonave.instance('$.store..price.round()', options);
var result = jp(example);
console.log(result); // [ 9, 13, 9, 23, 20 ]

It is also possible to define functions during the evaluation call

var round = function (obj) {
    return Math.round(obj);
};

var jp = jsonave.instance('$.store..price.round()');
var result = jp(example, {
    round: round
});
console.log(result); // [ 9, 13, 9, 23, 20 ]

License

Licensed under Apache 2.0.