Copys own enumerable properties of child and descendant object of source objects to destination object for each destination properties is undefined or null.

Usage no npm install needed!

<script type="module">
  import favPropDefaultsDeep from 'https://cdn.skypack.dev/@fav/prop.defaults-deep';


@fav/prop.defaults-deep NPM MIT License Build Status Build Status Coverage status

Copys enumerable own properties of child and descendants of source objects to destination object for destination properties which are undefined or null.

"fav" is an abbreviation of "favorite" and also the acronym of "for all versions". This package is intended to support all Node.js versions and many browsers as possible. At least, this package supports Node.js >= v0.10 and major Web browsers: Chrome, Firefox, IE11, Edge, Vivaldi and Safari.


To install from npm:

$ npm install --save @fav/prop.defaults-deep

NOTE: npm < 2.7.0 does not support scoped package, but old version Node.js supports it. So when you use such older npm, you should download this package from github.com, and move it in node_modules/@fav/prop.defaults-deep/ directory manually.


For Node.js:

var defaultsDeep = require('@fav/prop.defaults-deep');
defaultsDeep({ a: 1, b: { c: 2, d: 3 } }, { a: 10, b: { c: 20, e: 40 }, f: 50 });
// => { a: 1, b: { c: 2, d: 3, e: 40 }, f: 50 }

For Web browsers:

<script src="fav.prop.defaults-deep.min.js"></script>
var defaultsDeep = fav.prop.defaultsDeep;
defaultsDeep({ a: 1, b: { c: 2, d: 3 } }, { a: 10, b: { c: 20, e: 40 }, f: 50 });
// => { a: 1, b: { c: 2, d: 3, e: 40 }, f: 50 }


defaultsDeep(dest [, ...src]) : object

Copys enumerable own properties (both keys and symbols) of child and descendant objects of a source object to a destination object when each property value is null or undefined. If a property value of a source object is null or undefined, the property is not copied.

NOTE: This function does not throw an error when copying a source property to a destination property which is read only.


Parameter Type Description
dest object The destination object.
src object The source object(s).


The destination object.

Type: object


Node.js (4〜)

Platform 4 5 6 7 8 9 10

io.js (1〜3)

Platform 1 2 3

Node.js (〜0.12)

Platform 0.8 0.9 0.10 0.11 0.12

Web browsers

Platform Chrome Firefox Vivaldi Safari Edge IE11
macOS -- --
Windows10 --
Linux -- -- --


Copyright (C) 2017-2018 Takayuki Sato

This program is free software under MIT License. See the file LICENSE in this distribution for more details.