sindresorhus / filter-obj

Filter object keys and values into a new object

filter-obj

Filter object keys and values into a new object

Install

npm install filter-obj

Usage

import {includeKeys, excludeKeys} from 'filter-obj';

const object = {
	foo: true,
	bar: false
};

const newObject = includeKeys(object, (key, value) => value === true);
//=> {foo: true}

const newObject2 = includeKeys(object, ['bar']);
//=> {bar: false}

const newObject = excludeKeys(object, (key, value) => value === true);
//=> {bar: false}

const newObject3 = excludeKeys(object, ['bar']);
//=> {foo: true}

API

includeKeys(source, filter)

includeKeys(source, keys)

excludeKeys(source, filter)

excludeKeys(source, keys)

source

Type: object

The source object to filter properties from.

filter

Type: (sourceKey: string | symbol, sourceValue: unknown, source: object) => boolean

A predicate function that determines whether a property should be filtered.

keys

Type: Array<string | symbol>

An array of property keys to be filtered.

Related

• map-obj - Map object keys and values into a new object

filter-obj's Issues

Why use this over lodash/underscore _.pick?

I believe lodash.pick includes the same functionality as this module describes. I don't want to sound like hater, but I think there are enough utility libraries and reinventing the wheel isn't such a good idea.

Add a { deep: true } option

Just like map-obj and camelcase-keys.

Symbol properties should be kept

The README documents that symbol properties are not kept. However, this leads to some behavior that users might not expect:

const symbol = Symbol('example')
const obj = { [symbol]: true, a: 1, b: 2 }
const objCopy = excludeKeys(obj, ['b'])
objCopy[symbol] // undefined. Unexpected: the consumer only wanted to exclude 'b'

const objCopyTwo = includeKeys(obj, [symbol, 'a'])
objCopyTwo[symbol] // undefined. Unexpected: the consumer intended to keep symbol

I can submit a PR.

How Filter child objects present within root json object??

For Instance, let consider we have a JSON.

const person = {
  name: "John Doe",
  age: 27,
  kids:[
    {
      name: "James Doe",
      age: 7
    },
    {
      name: "Mary Doe",
      age: 7
    }
  ]
}

how to write the filter-obj so that I can get this solution.

filterObject(person, ['name', 'kids??'])
I tested it locally neither kids.name, kids[name], kids{name} worked!!

const person = {
  name: "John Doe",
  kids:[
    {
      name: "James Doe"
    },
    {
      name: "Mary Doe"
    }
  ]
}

Use `Object.getOwnPropertyDescriptors`

Instead of using Reflect.ownKeys and then Object.getOwnPropertyDescriptor (one), why not just get Object.getOwnPropertyDescriptors (multiple) and loop that?

Similarly, you could use Object.defineProperties instead of Object.defineProperty to create the object in one pass after mapping the result of the previous function.

Support key exclusions

Something like:

const filterObject = require('filter-obj');

filterObject({a: 1, b: 1, c: 1} {keys: ['!a']});
//=> {b: 1, c: 1}

Source: sindresorhus/query-string#282 (comment)

This changes whether a property is writable or configurable

The new properties returned by this library are always writable and configurable, even when the original properties were not. While non-writable or non-configurable properties are sometimes problematic, there are sometimes legitimate reasons for it. This seems to be an unintentional side effect.

const obj = Object.defineProperty({}, 'prop', { value: true, enumerable: true, writable: false, configurable: false })
const objCopy = includeKeys(obj, ['prop'])
console.log(Object.getOwnPropertyDescriptor(objCopy, 'prop'))
// { value: true, writable: true, enumerable: true, configurable: true }

Additionally, when a property is using get/set, they are currently removed.

const obj = Object.defineProperty({}, 'prop', { get: () => Math.random(), enumerable: true })
console.log(obj.prop, obj.prop) // Different random numbers
const objCopy = includeKeys(obj, ['prop'])
console.log(objCopy.prop, objCopy.prop) // Same random numbers

Instead of retrieving then copying the property values, the descriptors should be used instead.

filter-obj/index.js

Line 8 in 36e5f3a

const value = object[key];

filter-obj/index.js

Line 20 in 36e5f3a

const value = object[key];

Note: I can submit a PR.

Keeping non-enumerable properties

At the moment, non-enumerable properties are removed from the return value.

On one hand:

• Most functional utilities iterate on objects using standard for ... in, Object.keys(...), etc. which ignore non-enumerable properties. Object spreading { ...object } itself removes non-enumerable properties.
• The concept of a property being non-enumerable implies that it should not be iterated when being copied over.
• Non-enumerable properties are much less common on plain objects than on class instances, and this library is meant for plain objects.

On the other hand, some users might not expect non-enumerable properties removal as a side effect of this library. For example:

• excludeKeys(object, ['one']): this would remove object.two if it is non-enumerable, even though the user operation only intended to exclude object.one.
• includeKeys(object, ['one']): this would not include object.own if it is non-enumerable, even though the user explicitly requested to include it.
• For predicate functions, the user intent is less clear.

@sindresorhus What are your thoughts on this?

Allow any type of iterable

A consumer may want to use a Set instead of an array for filtering keys. We could allow for iterables to be provided.

Own `'__proto__'` keys assign to the prototype

If the input object contains an own property with the key '__proto__' and the filter does not reject it, rather than create a corresponding own property on the target object, filterObject sets the prototype of the target object to the property's value.

One possible fix is to use Object.defineProperty() for creating properties, rather than assignment.

I'll submit a PR adding test cases and the proposed fix.

Optional chaining is poor compatibility. may cause the error: uncaught syntaxerror unexpected token ' .'

Optional chaining has poor compatibility.
advice some compatiable method .