Merges the enumerable properties of two or more objects deeply.
UMD bundle is 718B minified+gzipped
As of version 5, ES5 is no longer natively supported
const x = {
foo: { bar: 3 },
array: [{
does: 'work',
too: [ 1, 2, 3 ]
}]
}
const y = {
foo: { baz: 4 },
quux: 5,
array: [{
does: 'work',
too: [ 4, 5, 6 ]
}, {
really: 'yes'
}]
}
const output = {
foo: {
bar: 3,
baz: 4
},
array: [{
does: 'work',
too: [ 1, 2, 3 ]
}, {
does: 'work',
too: [ 4, 5, 6 ]
}, {
really: 'yes'
}],
quux: 5
}
deepmerge(x, y) // => output
With npm do:
npm install deepmerge
deepmerge can be used directly in the browser without the use of package managers/bundlers as well: UMD version from unpkg.com.
deepmerge exposes a CommonJS entry point containing two functions:
const { deepmerge, deepmergeAll } = require('deepmerge')
The ESM entry point was dropped due to a Webpack bug.
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.
Merging creates a new object, so that neither x
or y
is modified.
Note: By default, arrays are merged by concatenating them.
Merges any number of objects into a single result object.
const foobar = { foo: { bar: 3 } }
const foobaz = { foo: { baz: 4 } }
const bar = { bar: 'yay!' }
deepmergeAll([ foobar, foobaz, bar ]) // => { foo: { bar: 3, baz: 4 }, bar: 'yay!' }
There are multiple ways to merge two arrays, below are a few examples but you can also create your own custom function.
Your arrayMerge
function will be called with three arguments: a target
array, the source
array, and an options
object with these properties:
isMergeableObject(value)
cloneUnlessOtherwiseSpecified(value, options)
Overwrites the existing array values completely rather than concatenating them:
const overwriteMerge = (destinationArray, sourceArray, options) => sourceArray
deepmerge(
[1, 2, 3],
[3, 2, 1],
{ arrayMerge: overwriteMerge }
) // => [3, 2, 1]
Combines objects at the same index in the two arrays.
This was the default array merging algorithm pre-version-2.0.0.
const combineMerge = (target, source, options) => {
const destination = target.slice()
source.forEach((item, index) => {
if (typeof destination[index] === 'undefined') {
destination[index] = options.cloneUnlessOtherwiseSpecified(item, options)
} else if (options.isMergeable(item)) {
destination[index] = deepmerge(target[index], item, options)
} else if (target.indexOf(item) === -1) {
destination.push(item)
}
})
return destination
}
deepmerge(
[{ a: true }],
[{ b: true }, 'ah yup'],
{ arrayMerge: combineMerge }
) // => [{ a: true, b: true }, 'ah yup']
By default, deepmerge clones properties of plain objects, and passes-by-reference all "special" kinds of instantiated objects.
You may not want this, if your objects are of special types, and you want to copy its properties instead of just copying the whole object.
You can accomplish this by passing in a function for the isMergeable
option.
For backwards compatibility, you can use the isMergeableObject
option for the same functionality.
To get the pre-version-5.0.0 behavior, you probably want to drop in is-mergeable-object
function mergeEverything(value) {
return value !== null && typeof value === 'object'
}
function SuperSpecial() {
this.special = 'oh yeah man totally'
}
const instantiatedSpecialObject = new SuperSpecial()
const target = {
someProperty: {
cool: 'oh for sure'
}
}
const source = {
someProperty: instantiatedSpecialObject
}
const defaultOutput = deepmerge(target, source)
defaultOutput.someProperty.cool // => undefined
defaultOutput.someProperty.special // => 'oh yeah man totally'
defaultOutput.someProperty instanceof SuperSpecial // => true
const customMergeOutput = deepmerge(target, source, {
isMergeable: mergeEverything
})
customMergeOutput.someProperty.cool // => 'oh for sure'
customMergeOutput.someProperty.special // => 'oh yeah man totally'
customMergeOutput.someProperty instanceof SuperSpecial // => false
Specifies a function which can be used to override the default merge behavior for a property, based on the property name.
The customMerge
function will be passed the key for each property, and should return the function which should be used to merge the values for that property.
It may also return undefined, in which case the default merge behaviour will be used.
const alex = {
name: {
first: 'Alex',
last: 'Alexson'
},
pets: ['Cat', 'Parrot']
}
const tony = {
name: {
first: 'Tony',
last: 'Tonison'
},
pets: ['Dog']
}
const mergeNames = (nameA, nameB) => `${nameA.first} and ${nameB.first}`
const options = {
customMerge: (key) => {
if (key === 'name') {
return mergeNames
}
}
}
const result = deepmerge(alex, tony, options)
result.name // => 'Alex and Tony'
result.pets // => ['Cat', 'Parrot', 'Dog']
Defaults to false
.
If clone
is true
then no deeply nested mergable object in the inputs will be in the resulting value.
With npm do:
npm test
MIT