What is deepmerge-ts?
The deepmerge-ts package is a TypeScript library designed to deeply merge two or more objects. It ensures type safety and is particularly useful for complex nested objects where shallow merging would not suffice.
What are deepmerge-ts's main functionalities?
Basic Deep Merge
This feature allows you to deeply merge two objects. In this example, obj1 and obj2 are merged such that the nested properties are combined.
const deepmerge = require('deepmerge-ts').default;
const obj1 = { a: 1, b: { c: 2 } };
const obj2 = { b: { d: 3 } };
const result = deepmerge(obj1, obj2);
console.log(result); // { a: 1, b: { c: 2, d: 3 } }
Array Merge
This feature allows you to merge arrays within objects. In this example, the arrays in obj1 and obj2 are concatenated.
const deepmerge = require('deepmerge-ts').default;
const obj1 = { a: [1, 2, 3] };
const obj2 = { a: [4, 5] };
const result = deepmerge(obj1, obj2);
console.log(result); // { a: [1, 2, 3, 4, 5] }
Custom Merge Function
This feature allows you to define custom merge functions for specific keys. In this example, the custom merge function concatenates arrays for the key 'a'.
const deepmerge = require('deepmerge-ts').default;
const customMerge = (key, options) => {
if (key === 'a') {
return (a, b) => a.concat(b);
}
return undefined;
};
const obj1 = { a: [1, 2, 3], b: { c: 2 } };
const obj2 = { a: [4, 5], b: { d: 3 } };
const result = deepmerge(obj1, obj2, { customMerge });
console.log(result); // { a: [1, 2, 3, 4, 5], b: { c: 2, d: 3 } }
Other packages similar to deepmerge-ts
deepmerge
The deepmerge package is a popular library for deep merging objects in JavaScript. It is similar to deepmerge-ts but does not provide TypeScript type safety out of the box.
lodash.merge
Lodash is a utility library that offers a wide range of functions, including deep merging with lodash.merge. While it is versatile and widely used, it is a larger library compared to deepmerge-ts, which is more specialized.
merge-deep
The merge-deep package is another library for deep merging objects. It is simpler and less feature-rich compared to deepmerge-ts, focusing solely on deep merging without additional customization options.
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Enterprise Users
deepmerge-ts
is available as part of the Tidelift Subscription.
Tidelift is working with the maintainers of deepmerge-ts
and a growing network of open source maintainers to ensure
your open source software supply chain meets enterprise standards now and into the future.
Learn more.
Installation
npm
npm install deepmerge-ts
pnpm add deepmerge-ts
yarn add deepmerge-ts
bun add deepmerge-ts
jsr
npx jsr add @rebeccastevens/deepmerge
deno add jsr:@rebeccastevens/deepmerge
bunx jsr add @rebeccastevens/deepmerge
Features
- Smart merging - High performance.
- Merged output has correct typing.
- Record merging support.
- Array merging support.
- Map and Set merging support.
- Customized merging.
Usage
Example using default config
import { deepmerge } from "deepmerge-ts";
const x = {
record: {
prop1: "value1",
prop2: "value2",
},
array: [1, 2, 3],
set: new Set([1, 2, 3]),
map: new Map([
["key1", "value1"],
["key2", "value2"],
]),
};
const y = {
record: {
prop1: "changed",
prop3: "value3",
},
array: [2, 3, 4],
set: new Set([2, 3, 4]),
map: new Map([
["key2", "changed"],
["key3", "value3"],
]),
};
const z = {
record: {
prop1: undefined,
prop3: undefined,
prop2: undefined,
prop4: undefined,
},
array: undefined,
set: undefined,
map: undefined,
};
const merged = deepmerge(x, y, z);
console.log(merged);
You can try out this example at
codesandbox.io.
Merging into a Target
You can use deepmergeInto
if you want to update a target object with the merge result instead of creating a new
object.
This function is best used with objects that are all of the same type.
Note: If the target object's type differs from the input objects, we'll assert that the target's type has changed
(this is not done automatically with deepmergeIntoCustom
).
Customized the Merging Process
We provide a customizer function for each of our main deepmerge functions: deepmergeCustom
and deepmergeIntoCustom
.
You can use these to customize the details of how values should be merged together.
See deepmerge custom docs for more details.
Performance
We use smart merging instead of the classic merging strategy which some alternative libraries use. This vastly improves
performance, both in execution time and memory usage.
Classic Merge (not what we do)
With classic merging, each input is merged with the next input until all inputs are merged.
This strategy has large performance issues when lots of items need to be merged.
Smart Merge (what we do)
With our smart merging, we look ahead to see what can be merged and only merge those things.
In addition to performance improvements, this strategy merges multiple inputs at once; allowing for benefits such as
taking averages of the inputs.
API
See API docs.