/JSONPath

A fork of JSONPath from http://goessner.net/articles/JsonPath/

Primary LanguageJavaScriptOtherNOASSERTION

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JSONPath Plus build status

Analyse, transform, and selectively extract data from JSON documents (and JavaScript objects).

jsonpath-plus expands on the original specification to add some additional operators and makes explicit some behaviors the original did not spell out.

Features

  • Compliant with the original jsonpath spec
  • Convenient additions or elaborations not provided in the original spec:
    • ^ for grabbing the parent of a matching item
    • ~ for grabbing property names of matching items (as array)
    • Type selectors for obtaining:
      • Basic JSON types: @null(), @boolean(), @number(), @string(), @array(), @object()
      • @integer()
      • The compound type @scalar() (which also accepts undefined and non-finite numbers when querying JavaScript objects as well as all of the basic non-object/non-function types)
      • @other() usable in conjunction with a user-defined otherTypeCallback
      • Non-JSON types that can nevertheless be used when querying non-JSON JavaScript objects (@undefined(), @function(), @nonFinite())
    • @path/@parent/@property/@parentProperty/@root shorthand selectors within filters
    • Escaping
      • ` for escaping remaining sequence
      • @['...']/?@['...'] syntax for escaping special characters within property names in filters
    • Documents $.. (getting all parent components)
  • ESM and UMD export formats
  • In addition to queried values, can return various meta-information including paths or pointers to the value, as well as the parent object and parent property name (to allow for modification).
  • Utilities for converting between paths, arrays, and pointers
  • Option to prevent evaluations permitted in the original spec or supply a sandbox for evaluated values.
  • Option for callback to handle results as they are obtained.

Benchmarking

jsonpath-plus is consistently performant with both large and small datasets compared to other json querying libraries per json-querying-performance-testing. You can verify these findings by running the project yourself and adding more perf cases.

Install

npm install jsonpath-plus

Setup

Node.js

const {JSONPath} = require('jsonpath-plus');

const result = JSONPath({path: '...', json});

Browser

For browser usage you can directly include dist/index-umd.js; no Browserify magic is necessary:

<!-- Polyfill recommended by Babel for items not covered for older
      browsers in dist -->
<script src="node_modules/core-js-bundle/minified.js"></script>

<script src="node_modules/jsonpath-plus/dist/index-umd.js"></script>
<script>
const result = JSONPath.JSONPath({path: '...', json: ...});
</script>

ESM (Modern browsers)

You may also use ES6 Module imports (for modern browsers):

<script type="module">
import {JSONPath} from './node_modules/jsonpath-plus/dist/index-es.js';
const result = JSONPath({path: '...', json: ...});
</script>

ESM (Bundlers)

Or if you are bundling your JavaScript (e.g., with Rollup), just use:

import {JSONPath} from 'jsonpath-plus';

const result = JSONPath({path: '...', json});

Usage

The full signature available is:

const result = JSONPath([options,] path, json, callback, otherTypeCallback);

The arguments path, json, callback, and otherTypeCallback can alternatively be expressed (along with any other of the available properties) on options.

Note that result will contain all items found (optionally wrapped into an array) whereas callback can be used if you wish to perform some operation as each item is discovered, with the callback function being executed 0 to N times depending on the number of independent items to be found in the result. See the docs below for more on JSONPath's available arguments.

Properties

The properties that can be supplied on the options object or evaluate method (as the first argument) include:

  • path (required) - The JSONPath expression as a (normalized or unnormalized) string or array
  • json (required) - The JSON object to evaluate (whether of null, boolean, number, string, object, or array type).
  • autostart (default: true) - If this is supplied as false, one may call the evaluate method manually.
  • flatten (default: false) - Whether the returned array of results will be flattened to a single dimension array.
  • resultType (default: "value") - Can be case-insensitive form of "value", "path", "pointer", "parent", or "parentProperty" to determine respectively whether to return results as the values of the found items, as their absolute paths, as JSON Pointers to the absolute paths, as their parent objects, or as their parent's property name. If set to "all", all of these types will be returned on an object with the type as key name.
  • sandbox (default: {}) - Key-value map of variables to be available to code evaluations such as filtering expressions. (Note that the current path and value will also be available to those expressions; see the Syntax section for details.)
  • wrap (default: true) - Whether or not to wrap the results in an array. If wrap is set to false, and no results are found, undefined will be returned (as opposed to an empty array when wrap is set to true). If wrap is set to false and a single non-array result is found, that result will be the only item returned (not within an array). An array will still be returned if multiple results are found, however. To avoid ambiguities (in the case where it is necessary to distinguish between a result which is a failure and one which is an empty array), it is recommended to switch the default to false.
  • preventEval (default: false) - Although JavaScript evaluation expressions are allowed by default, for security reasons (if one is operating on untrusted user input, for example), one may wish to set this option to true to throw exceptions when these expressions are attempted.
  • parent (default: null) - In the event that a query could be made to return the root node, this allows the parent of that root node to be returned within results.
  • parentProperty (default: null) - In the event that a query could be made to return the root node, this allows the parentProperty of that root node to be returned within results.
  • callback (default: (none)) - If supplied, a callback will be called immediately upon retrieval of an end point value. The three arguments supplied will be the value of the payload (according to resultType), the type of the payload (whether it is a normal "value" or a "property" name), and a full payload object (with all resultTypes).
  • otherTypeCallback (default: <A function that throws an error when @other() is encountered>) - In the current absence of JSON Schema support, one can determine types beyond the built-in types by adding the operator @other() at the end of one's query. If such a path is encountered, the otherTypeCallback will be invoked with the value of the item, its path, its parent, and its parent's property name, and it should return a boolean indicating whether the supplied value belongs to the "other" type or not (or it may handle transformations and return false).

Instance methods

  • evaluate(path, json, callback, otherTypeCallback) OR evaluate({path: <path>, json: <json object>, callback: <callback function>, otherTypeCallback: <otherTypeCallback function>}) - This method is only necessary if the autostart property is set to false. It can be used for repeated evaluations using the same configuration. Besides the listed properties, the latter method pattern can accept any of the other allowed instance properties (except for autostart which would have no relevance here).

Class properties and methods

  • JSONPath.cache - Exposes the cache object for those who wish to preserve and reuse it for optimization purposes.
  • JSONPath.toPathArray(pathAsString) - Accepts a normalized or unnormalized path as string and converts to an array: for example, ['$', 'aProperty', 'anotherProperty'].
  • JSONPath.toPathString(pathAsArray) - Accepts a path array and converts to a normalized path string. The string will be in a form like: $['aProperty']['anotherProperty][0]. The JSONPath terminal constructions ~ and ^ and type operators like @string() are silently stripped.
  • JSONPath.toPointer(pathAsArray) - Accepts a path array and converts to a JSON Pointer. The string will be in a form like: /aProperty/anotherProperty/0 (with any ~ and / internal characters escaped as per the JSON Pointer spec). The JSONPath terminal constructions ~ and ^ and type operators like @string() are silently stripped.

Syntax through examples

Given the following JSON, taken from http://goessner.net/articles/JsonPath/:

{
"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
  }
}
}

and the following XML representation:

<store>
    <book>
        <category>reference</category>
        <author>Nigel Rees</author>
        <title>Sayings of the Century</title>
        <price>8.95</price>
    </book>
    <book>
        <category>fiction</category>
        <author>Evelyn Waugh</author>
        <title>Sword of Honour</title>
        <price>12.99</price>
    </book>
    <book>
        <category>fiction</category>
        <author>Herman Melville</author>
        <title>Moby Dick</title>
        <isbn>0-553-21311-3</isbn>
        <price>8.99</price>
    </book>
    <book>
        <category>fiction</category>
        <author>J. R. R. Tolkien</author>
        <title>The Lord of the Rings</title>
        <isbn>0-395-19395-8</isbn>
        <price>22.99</price>
    </book>
    <bicycle>
        <color>red</color>
        <price>19.95</price>
    </bicycle>
</store>

Please note that the XPath examples below do not distinguish between retrieving elements and their text content (except where useful for comparisons or to prevent ambiguity).

XPath JSONPath Result Notes
/store/book/author $.store.book[*].author The authors of all books in the store Can also be represented without the $. as store.book[*].author (though this is not present in the original spec); note that some character literals ($ and @) require escaping, however
//author $..author All authors
/store/* $.store.* All things in store, which are its books (a book array) and a red bicycle (a bicycle object).
/store//price $.store..price The price of everything in the store.
//book[3] $..book[2] The third book (book object)
//book[last()] $..book[(@.length-1)]
$..book[-1:]		 The last book in order. To access a property with a special character, utilize [(@['...'])] for the filter (this particular feature is not present in the original spec)
//book[position()<3] $..book[0,1]
$..book[:2]		 The first two books
//book/*[self::category|self::author] or //book/(category,author) in XPath 2.0 $..book[0][category,author] The categories and authors of all books
//book[isbn] $..book[?(@.isbn)] Filter all books with an ISBN number To access a property with a special character, utilize [?@['...']] for the filter (this particular feature is not present in the original spec)
//book[price<10] $..book[?(@.price<10)] Filter all books cheaper than 10
//*[name() = 'price' and . != 8.95] $..*[?(@property === 'price' && @ !== 8.95)] Obtain all property values of objects whose property is price and which does not equal 8.95 With the bare @ allowing filtering objects by property value (not necessarily within arrays), you can add ^ after the expression to get at the object possessing the filtered properties
/ $ The root of the JSON object (i.e., the whole object itself) To get a literal $ (by itself or anywhere in the path), you must use the backtick escape
//*/*|//*/*/text() $..* All Elements (and text) beneath root in an XML document. All members of a JSON structure beneath the root.
//* $.. All Elements in an XML document. All parent components of a JSON structure including root. This behavior was not directly specified in the original spec
//*[price>19]/.. $..[?(@.price>19)]^ Parent of those specific items with a price greater than 19 (i.e., the store value as the parent of the bicycle and the book array as parent of an individual book) Parent (caret) not present in the original spec
/store/*/name() (in XPath 2.0) $.store.*~ The property names of the store sub-object ("book" and "bicycle"). Useful with wildcard properties. Property name (tilde) is not present in the original spec
/store/book[not(. is /store/book[1])] (in XPath 2.0) $.store.book[?(@path !== "$['store']['book'][0]")] All books besides that at the path pointing to the first @path not present in the original spec
//book[parent::*/bicycle/color = "red"]/category $..book[?(@parent.bicycle && @parent.bicycle.color === "red")].category Grabs all categories of books where the parent object of the book has a bicycle child whose color is red (i.e., all the books) @parent is not present in the original spec
//book/*[name() != 'category'] $..book.*[?(@property !== "category")] Grabs all children of "book" except for "category" ones @property is not present in the original spec
//book/*[position() != 0] $..book[?(@property !== 0)] Grabs all books whose property (which, being that we are reaching inside an array, is the numeric index) is not 0 @property is not present in the original spec
/store/*/*[name(parent::*) != 'book'] $.store.*[?(@parentProperty !== "book")] Grabs the grandchildren of store whose parent property is not book (i.e., bicycle's children, "color" and "price") @parentProperty is not present in the original spec
//book[count(preceding-sibling::*) != 0]/*/text() $..book.*[?(@parentProperty !== 0)] Get the property values of all book instances whereby the parent property of these values (i.e., the array index holding the book item parent object) is not 0 @parentProperty is not present in the original spec
//book[price = /store/book[3]/price] $..book[?(@.price === @root.store.book[2].price)] Filter all books whose price equals the price of the third book @root is not present in the original spec
//book/../*[. instance of element(*, xs:decimal)] (in XPath 2.0) $..book..*@number() Get the numeric values within the book array @number(), the other basic types (@boolean(), @string()), other low-level derived types (@null(), @object(), @array()), the JSONSchema-added type, @integer(), the compound type @scalar() (which also accepts undefined and non-finite numbers for JavaScript objects as well as all of the basic non-object/non-function types), the type, @other(), to be used in conjunction with a user-defined callback (see otherTypeCallback) and the following non-JSON types that can nevertheless be used with JSONPath when querying non-JSON JavaScript objects (@undefined(), @function(), @nonFinite()) are not present in the original spec
` (e.g., `$ to match a property literally named $) Escapes the entire sequence following (to be treated as a literal) ` is not present in the original spec; to get a literal backtick, use an additional backtick to escape

Any additional variables supplied as properties on the optional "sandbox" object option are also available to (parenthetical-based) evaluations.

Potential sources of confusion for XPath users

  1. In JSONPath, a filter expression, in addition to its @ being a reference to its children, actually selects the immediate children as well, whereas in XPath, filter conditions do not select the children but delimit which of its parent nodes will be obtained in the result.
  2. In JSONPath, array indexes are, as in JavaScript, 0-based (they begin from 0), whereas in XPath, they are 1-based.
  3. In JSONPath, equality tests utilize (as per JavaScript) multiple equal signs whereas in XPath, they use a single equal sign.

Ideas

  1. Support OR outside of filters (as in XPath |) and grouping.
  2. Create syntax to work like XPath filters in not selecting children?
  3. Allow option for parentNode equivalent (maintaining entire chain of parent-and-parentProperty objects up to root)

Development

Running the tests on Node:

npm test

For in-browser tests:

  • Serve the js/html files:
npm run browser-test

License

MIT License.