The deepmerge npm package is a library for deep (recursive) merging of Javascript objects. It is useful for combining objects with nested structures, such as configuration settings or state objects in applications.

What are deepmerge's main functionalities?

Merging two objects

This feature allows you to merge two objects deeply. Properties from the second object will be added to the first, and if properties are objects themselves, they will be merged recursively.

{"const merge = require('deepmerge');
const x = { foo: { bar: 3 } };
const y = { foo: { baz: 4 } };
const z = merge(x, y);
console.log(z); // { foo: { bar: 3, baz: 4 } }"}

Merging with array concatenation

This feature allows you to specify how arrays are merged. By default, arrays are merged by concatenation, but you can provide a custom arrayMerge function.

{"const merge = require('deepmerge');
const x = { foo: [1, 2, 3] };
const y = { foo: [4, 5, 6] };
const z = merge(x, y, { arrayMerge: (destinationArray, sourceArray) => destinationArray.concat(sourceArray) });
console.log(z); // { foo: [1, 2, 3, 4, 5, 6] }"}

Merging with array replacement

This feature allows you to replace the destination array with the source array instead of merging or concatenating them.

{"const merge = require('deepmerge');
const x = { foo: [1, 2, 3] };
const y = { foo: [4, 5, 6] };
const z = merge(x, y, { arrayMerge: (destinationArray, sourceArray) => sourceArray });
console.log(z); // { foo: [4, 5, 6] }"}

Merging with custom options

This feature allows you to provide custom merge functions to handle the merging process according to your specific requirements.

{"const merge = require('deepmerge');
const x = { foo: { bar: 3 } };
const y = { foo: { bar: 4, baz: 5 } };
const overwriteMerge = (destinationArray, sourceArray, options) => sourceArray;
const z = merge(x, y, { arrayMerge: overwriteMerge });
console.log(z); // { foo: { bar: 4, baz: 5 } }"}

Other packages similar to deepmerge

Readme

Source

deepmerge

Merge the enumerable attributes of two objects deeply.

example

var util = require('util')
var merge = require('deepmerge')

var x = { foo: { bar: 3 },
  array: [ { does: 'work', too: [ 1, 2, 3 ] } ] }
var y = { foo: { baz: 4 },
  quux: 5,
  array: [ { does: 'work', too: [ 4, 5, 6 ] }, { really: 'yes' } ] }

console.log(util.inspect(merge(x, y), false, null))

output:

{ foo: { bar: 3, baz: 4 },
  array: [ { does: 'work', too: [ 1, 2, 3, 4, 5, 6 ] }, { really: 'yes' } ],
  quux: 5 }

methods

var merge = require('deepmerge')

merge(x, y)

Merge two objects x and y deeply, returning a new merged object with the elements from both x and y.

If an element at the same key is present for both x and y, the value from y will appear in the result.

The merge is immutable, so neither x nor y will be modified.

The merge will also merge arrays and array values.

install

With npm do:

npm install deepmerge

test

With npm do:

npm test

FAQs

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Last updated on 31 May 2013

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