is-plain

v1.1.0

Published

3 years ago

Test if a value is a plain object

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is-plain

Tests if a value is a plain object. That is:

an object created using new Object()
or, an object without a prototype Object.create(null)
or, an object created using the literal notation {}

Installation

# using npm
npm install --save is-plain

# using yarn
yarn add is-plain

Usage

import isPlain from 'is-plain';

isPlain({ foo: 'bar' });
//=> true

isPlain(Object.create(null));
//=> true

isPlain(new Object());
//=> true

class Foo {}
isPlain(new Foo());
//=> false

isPlain([1, 2, 3]);
//=> false

isPlain(null);
//=> false

isPlain(Promise.resolve());
//=> false

Comparison with Other Libraries

There are already similar libraries available to test if a value is a plain object. Some of these libraries are very widely adopted. To name a few:

So, why need is-plain when other solutions already exist?

Small Package Size

is-plain is only 140 bytes minzipped.

The following is a size comparison between is-plain and other popular libraries ranked by their minified size:

Edge Cases Other Libraries Missed

While is-plain is very comparable to is-plain-obj in both size and logic (is-plain being smaller by 3 bytes), the size wasn't the the only motive. Most importantly, what I wanted to address is some of the edge cases the other libraries are missing.

The following are some of the cases that causes inconsistent, arguably incorrect, results when one of the other three libraries is used (note that in all of the following cases, is-plain considers these objects to be plain objects).

Case 1

// an object without a prototype
const value = Object.create(null);

| | | is value a plain object? | | --- | ----------------------------- | -------------------------- | | | is-plain (this package) | true | | | is-plain-obj | true | | ⚠️ | is-plain-object | false | | | lodash.isplainobject | true |

Case 2

// an object with an empty prototype
const value = Object.create({});

| | | is value a plain object? | | --- | ----------------------------- | -------------------------- | | | is-plain (this package) | true | | ⚠️ | is-plain-obj | false | | | is-plain-object | true | | ⚠️ | lodash.isplainobject | false |

Case 3

// an object with a prototype whose constructor is Object
const value = Object.create({ constructor: Object });

Case 4

// an object literal with own property 'constructor'
const value = {
  constructor: Foo,
};

Case 5

// an object literal with a '__proto__' property as an object
const value = {
  __proto__: {},
};

Case 6

// an instance of a prototype whose constructor is Object
function ObjectConstructor() {}
ObjectConstructor.prototype.constructor = Object;
const value = new ObjectConstructor();

License

MIT