extend

What is extend?

The extend npm package is a utility for shallowly or deeply copying the properties of one object to another. It is commonly used to extend the properties of an object with the properties of one or more other objects.

What are extend's main functionalities?

Shallow extend

This feature allows you to copy the properties of one or more source objects to a target object without deep copying. Properties in the target object will be overwritten by properties in the sources if they have the same key.

{"var extend = require('extend');
var obj1 = { a: 1 };
var obj2 = { b: 2 };
var extended = extend(obj1, obj2);
// Result: { a: 1, b: 2 }"}

Deep extend

This feature allows you to perform a deep copy of the properties of one or more source objects into a target object. Nested objects and arrays will be recursively copied, rather than just copying the reference.

{"var extend = require('extend');
var obj1 = { a: { b: 1 } };
var obj2 = { a: { c: 2 } };
var extended = extend(true, obj1, obj2);
// Result: { a: { b: 1, c: 2 } }"}

Other packages similar to extend

lodash.merge

Lodash's merge function is similar to extend's deep extend feature. It recursively merges own and inherited enumerable string keyed properties of source objects into the destination object, also merging arrays and array-like objects.

object-assign

Object-assign is a polyfill for the Object.assign() method which copies enumerable and own properties from a source object to a target object. It is similar to extend's shallow copy feature but does not support deep copying.

deep-extend

Deep-extend is an npm package that provides deep copy functionality similar to extend's deep extend feature. It allows for deep copying of the enumerable properties of one or more source objects into a target object.

README

extend() for Node.js

node-extend is a port of the classic extend() method from jQuery. It behaves as you expect. It is simple, tried and true.

Notes:

• Since Node.js >= 4, Object.assign now offers the same functionality natively (but without the "deep copy" option). See ECMAScript 2015 (ES6) in Node.js.
• Some native implementations of Object.assign in both Node.js and many browsers (since NPM modules are for the browser too) may not be fully spec-compliant. Check object.assign module for a compliant candidate.

Installation

This package is available on npm as: extend

npm install extend

Usage

Syntax: extend ( [deep], target, object1, [objectN] )

Extend one object with one or more others, returning the modified object.

Example:

var extend = require('extend');
extend(targetObject, object1, object2);

Keep in mind that the target object will be modified, and will be returned from extend().

If a boolean true is specified as the first argument, extend performs a deep copy, recursively copying any objects it finds. Otherwise, the copy will share structure with the original object(s). Undefined properties are not copied. However, properties inherited from the object's prototype will be copied over. Warning: passing false as the first argument is not supported.

Arguments

• deep Boolean (optional) If set, the merge becomes recursive (i.e. deep copy).
• target Object The object to extend.
• object1 Object The object that will be merged into the first.
• objectN Object (Optional) More objects to merge into the first.

License

node-extend is licensed under the MIT License.

Acknowledgements

All credit to the jQuery authors for perfecting this amazing utility.

Ported to Node.js by Stefan Thomas with contributions by Jonathan Buchanan and Jordan Harband.