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@fastify/deepmerge
Advanced tools
Merges the enumerable properties of two or more objects deeply.
Merges the enumerable properties of two or more objects deeply. Fastest implementation of deepmerge, see section 'Benchmarks'.
npm i @fastify/deepmerge
The module exports a function, which provides a function to deepmerge Objects.
deepmerge(options)
options
is optional and can contain following values
symbols
(boolean
, optional) - should also merge object-keys which are symbols, default is falseall
(boolean
, optional) - merges all parameters, default is falsemergeArray
(function
, optional) - provide a function, which returns a function to add custom array merging functioncloneProtoObject
(function
, optional) - provide a function, which must return a clone of the object with the prototype of the objectconst deepmerge = require('@fastify/deepmerge')()
const result = deepmerge({a: 'value'}, { b: 404 })
console.log(result) // {a: 'value', b: 404 }
const deepmerge = require('@fastify/deepmerge')({ all: true })
const result = deepmerge({a: 'value'}, { b: 404 }, { a: 404 })
console.log(result) // {a: 404, b: 404 }
The default mode to merge Arrays is to concat the source-Array to the target-Array.
const target = [1, 2, 3]
const source = [4, 5, 6]
const deepmerge = require('@fastify/deepmerge')()
const result = deepmerge(target, source)
console.log(result) // [1, 2, 3, 4, 5, 6]
To overwrite the default behaviour regarding merging Arrays, you can provide a function to the
mergeArray
option of the deepmerge-function. The function provided to mergeArray
gets an options-parameter passed, which is an Object containing the following keys and values.
clone: (value: any) => any;
isMergeableObject: (value: any) => any;
deepmerge: DeepMergeFn;
getKeys: (value: object) => string[];
The mergeArray
-Function needs to return the actual Array merging function, which accepts two parameters of type
Array, and returns a value.
Example 1: Replace the target-Array with a clone of the source-Array.
function replaceByClonedSource(options) {
const clone = options.clone
return function (target, source) {
return clone(source)
}
}
const deepmerge = require('@fastify/deepmerge')({ mergeArray: replaceByClonedSource })
const result = deepmerge([1, 2, 3], [4, 5, 6])
console.log(result) // [4, 5, 6]
Example 2: Merge each element of the source-Array with the element at the same index-position of the target-Array.
function deepmergeArray(options) {
const deepmerge = options.deepmerge
const clone = options.clone
return function (target, source) {
let i = 0
const tl = target.length
const sl = source.length
const il = Math.max(target.length, source.length)
const result = new Array(il)
for (i = 0; i < il; ++i) {
if (i < sl) {
result[i] = deepmerge(target[i], source[i])
} else {
result[i] = clone(target[i])
}
}
return result
}
}
// default behaviour
const deepmergeConcatArray = require('@fastify/deepmerge')()
const resultConcatArray = deepmergeConcatArray([{ a: [1, 2, 3 ]}], [{b: [4, 5, 6]}])
console.log(resultConcatArray) // [ { a: [ 1, 2, 3 ]}, { b: [ 4, 5, 6 ] } ]
// modified behaviour
const deepmergeDeepmergeArray = require('@fastify/deepmerge')({ mergeArray: deepmergeArray })
const resultDeepmergedArray = deepmergeDeepmergeArray([{ a: [1, 2, 3 ]}], [{b: [4, 5, 6]}])
console.log(resultDeepmergedArray) // [ { a: [ 1, 2, 3 ], b: [ 4, 5, 6 ] } ]
Merging objects with prototypes, such as Streams or Buffers, are not supported by default.
You can provide a custom function to let this module deal with the object that has a prototype
(JSON object excluded).
function cloneByReference (source) {
return source
}
const deepmergeByReference = require('@fastify/deepmerge')({
cloneProtoObject: cloneByReference
})
const result = deepmergeByReference({}, { stream: process.stdout })
console.log(result) // { stream: <ref *1> WriteStream }
The benchmarks are available in the benchmark-folder.
npm run bench
- benchmark various use cases of deepmerge:
@@fastify/deepmerge: merge regex with date x 1,256,523,040 ops/sec ±0.16% (92 runs sampled)
@fastify/deepmerge: merge object with a primitive x 1,256,082,915 ops/sec ±0.25% (97 runs sampled)
@fastify/deepmerge: merge two arrays containing strings x 25,392,605 ops/sec ±0.22% (97 runs sampled)
@fastify/deepmerge: two merge arrays containing objects x 1,655,426 ops/sec ±0.65% (96 runs sampled)
@fastify/deepmerge: merge two flat objects x 15,571,029 ops/sec ±0.45% (96 runs sampled)
@fastify/deepmerge: merge nested objects x 7,601,328 ops/sec ±0.31% (96 runs sampled)
npm run bench:compare
- comparison of @fastify/deepmerge with other popular deepmerge implementation:
@fastify/deepmerge x 605,343 ops/sec ±0.87% (96 runs sampled)
deepmerge x 20,312 ops/sec ±1.06% (92 runs sampled)
merge-deep x 83,167 ops/sec ±1.30% (94 runs sampled)
ts-deepmerge x 175,977 ops/sec ±0.57% (96 runs sampled)
deepmerge-ts x 174,973 ops/sec ±0.44% (93 runs sampled)
lodash.merge x 89,213 ops/sec ±0.70% (98 runs sampled)
Licensed under MIT.
FAQs
Merges the enumerable properties of two or more objects deeply.
The npm package @fastify/deepmerge receives a total of 775,360 weekly downloads. As such, @fastify/deepmerge popularity was classified as popular.
We found that @fastify/deepmerge demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 0 open source maintainers collaborating on the project.
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