@sagold/json-pointer

json-pointer implementation following RFC 6901 to work with serializable paths into javascript data structures.

api | usage examples | fragment identifier | breaking changes

install

yarn add @sagold/json-pointer

usage

import { get, set, remove } from '@sagold/json-pointer';
const data = {};

get(data, '/path/to/nested/item'); // undefined
set(data, '/path/to/nested/item', 123); // { path: { to: { nested: { item: 123 }}}
remove(data, '/path/to/nested/item'); // { path: { to: { nested: { }}}

API

As the error handling is not further specified, this implementation will return undefined for any invalid pointer/missing data, making it very convenient to work with uncertain data.

method	description
get(data, pointer) -> value	returns the value at given pointer
set(data, pointer, value) -> data	sets the value at the given path
remove(data, pointer) -> data	removes a property from data
join(...pointers) -> pointer	joins multiple pointers to a single one
split(pointer) -> [array]	returns a json-pointer as an array
splitLast(pointer) -> [pointer, property]	returns parent-pointer and last property

The methods get, set, remove and join also accept a list of properties as pointer. Using join with a list of properties, its signature changes to join(properties:string[], isURI=false) -> string

Usage Examples

get

get(data:object|array, pointer:string|array, defaultValue:any) -> value:any

returns nested values

import pointer from '@sagold/json-pointer';
const data = {
    parent: {
        child: {
            title: 'title of child'
        }
    }
}

const titleOfChild = pointer.get(data, '/parent/child/title'); // output: 'title of child'
console.log(pointer.get(data, '/parent/missing/path')); // output: undefined

and may optionally return a default value with

import pointer from '@sagold/json-pointer';
const value = pointer.get({}, "/invalid/value", 42);
console.log(value); // output: 42

get also accepts a list of properties as pointer (e.g. split-result)

const titleOfChild = pointer.get(data, ['parent', 'child', 'title']); // output: 'title of child'
console.log(pointer.get(data, ['parent', 'missing', 'path'])); // output: undefined

set

set(data:object|array, pointer:string|array, value:any) -> data:object|array

changes a nested value

import pointer from '@sagold/json-pointer';

var data = {
    parent: {
        children: [
            {
                title: 'title of child'
            }
        ]
    }
};

pointer.set(data, '/parent/children/1', { title: 'second child' });
console.log(data.parent.children.length); // output: 2

and may be used to build data

import pointer from '@sagold/json-pointer';
const data = pointer.set({}, '/list/[]/value', 42);
console.log(data); // output: { list: [ { value: 42 } ] }

set also accepts a list of properties as pointer (e.g. split-result)

import pointer from '@sagold/json-pointer';
const data = pointer.set({}, ['list', '[]', 'value'], 42);
console.log(data); // output: { list: [ { value: 42 } ] }

behaviour using set

set will create arrays when encountering a number

pointer.set({}, ['list', '1', 'value'], 42);
// { list: [undefined, { value: 42 }] }

alternatively you may use array-syntax [index]

pointer.set({}, ['list', '[1]', 'value'], 42);
// { list: [undefined, { value: 42 }] }

append items using empty array syntax []

pointer.set({ list: [1, 2] }, ['list', '[]', 'value'], 42);
// { list: [1, 2, { value: 42 }] }

create object using object syntax {index}

pointer.set({}, ['list', '{1}', 'value'], 42);
// { list: { 1: { value: 42 } }

⚠️ set prefers existing data-type over specified data-types. For example: Setting an object for an existing array, will keep the object intact:

pointer.set({ list: []}, ['list', '{0}', 'value'], 42);
// { list: [{ value: 42 }] }

array

Per default set creates objects for each each missing data. Thus, a pointer to /list/1 will create an object with { list: { 1: {} } }. If you want to specify array-data you will need to wrap the array-index in array-brackets:

pointer.set({}, '/list/[1]', 42);
// { list: [, 42] }

Omitting the index from the array-brackets will append the item:

pointer.set({}, '/list/[]', 42);
// { list: [42] }

which also works for existing lists:

pointer.set({ list: ["first"] }, '/list/[]', 42);
// { list: ["first", 42] }

remove

remove(data:object|array, pointer:string|array) -> data:object|array

deletes a nested property or item

import pointer from '@sagold/json-pointer';
const data = pointer.remove({ parent: { arrayOrObject: [ 0, 1 ] }}, '/parent/arrayOrObject/1');
console.log(data.parent.arrayOrObject); // output: [0]

remove also accepts a list of properties as pointer (e.g. split-result)

import pointer from '@sagold/json-pointer';
const data = pointer.remove({ parent: { arrayOrObject: [ 0, 1 ] }}, ['parent', 'arrayOrObject', '1']);
console.log(data.parent.arrayOrObject); // output: [0]

split

split(pointer:string) -> properties:array

returns a json-pointer as a list of (escaped) properties

import pointer from '@sagold/json-pointer';
const list = pointer.split('/parent/arrayOrObject/1');
console.log(list); // output: ['parent', 'arrayOrObject', '1']

In order to resolve a list of properties, you can directly pass the list to get, set or remove

import pointer from '@sagold/json-pointer';
const data = { a: { b: true } };
const list = pointer.split('/a/b');
console.log(pointer.get(data, list)); // output: true

splitLast

splitLast(pointer:string) -> [pointer, property]

separates json-pointers last property and returns both values as [parent-pointer, property]

import pointer from '@sagold/json-pointer';
const [parent, property] = pointer.splitLast('/parent/arrayOrObject/1');
console.log(parent); // output: '/parent/arrayOrObject'
console.log(property); // output: '1'

join

join(...pointers:string[]) -> pointer:string

joins all arguments to a valid json pointer

import pointer from '@sagold/json-pointer';
const key = 'my key';
console.log(pointer.join('root', key, '/to/target')); // output: '/root/my key/to/target'

and joins relative pointers as expected

import pointer from '@sagold/json-pointer';
console.log(pointer.join('/path/to/value', '../object')); // output: '/path/to/object'

in order to join an array received from split, you can use join(properties:string[], isURI=false) -> string to retrieve a valid pointer

import pointer from '@sagold/json-pointer';
const list = pointer.split('/my/path/to/child');
list.pop();
console.log(pointer.join(list)); // output: '/my/path/to'

To join an array of pointers, you must use it with join(...pointers) or all pointers will be treated as properties:

import pointer from '@sagold/json-pointer';
const path = pointer.join(...['/path/to/value', '../object']);
console.log(path); // output: '/path/to/object'

// passing the array directly, will treat each entry as a property, which will be escaped and resolves to:
pointer.join(['/path/to/value', '../object']); // output: '/~1path~1to~1value/..~1object'

Fragment identifier

All methods support a leading uri fragment identifier (#), which will ensure that property-values are uri decoded when resolving the path within data. This also ensures that any pointer is returned uri encoded with a leading #. e.g.

import pointer from '@sagold/json-pointer';

// get
const value = pointer.get({ 'my value': true }, '#/my%20value');
console.log(value); // output: true

// join
const pointer = pointer.join('#/my value/to%20parent', '../to~1child');
console.log(pointer); // output: '#/my%20value/to~1child'

// join an array of properties
const uriPointer = pointer.join(['my value', 'to~1child'], isURI = true);
console.log(uriPointer); // output: '#/my%20value/to~1child'

Additionally join(...pointers, isURI) may be used to enforce the pointer type, which is helpful in sanitizing inputs

const uriPointer = pointer.join('my pointer', 'to', 'property', isURI = true);
console.log(uriPointer); // output: '#/my%20pointer/to/property'

const uriSimple = pointer.join('/my pointer/to/property', isURI = true);
console.log(uriSimple); // output: '#/my%20pointer/to/property'

const pointer = pointer.join('#/my pointer', 'to', 'property', isURI = false);
console.log(pointer); // output: '/my pointer/to/property'

Breaking Changes

• 2025/01/14 with v7
  • pointer.set creates arrays using numbers as properties /1 when the data is null or an array (previously created objects)
  • pointer.set creates objects for numbers when using object-syntax /{1} (previously unsupported)
• 2024/04/06 with v6, selection of empty properties is supported:
  • "/" now selects an empty property (previously root-pointer)
  • "a//b" is now a valid pointer to "a" » "" » "b"
  • join no longer removes double slashes when joining join("/a/", "/b") » "/a//b"
• 2022/12/02 with v5, package has been renamed to json-pointer and published under @sagold/json-pointer
• 2020/11/09 with v4, pointer.delete has been renamed to remove