deepmerge-json
Advanced tools
A simple library to deep merge json files with array operations. Hugely inspired by the awesome deepmerge project.
Note that you can use to merge javascript objects, but the main reason this library was created was to merge json files with optional special operations for array merging.
Sometimes you need a deeply copied objects. Sometimes you need to alter these objects to make them more extensible and generic, specially when you are using convention over configuration or convention over code patterns.
The objective of this library is to help you with these situations being really simple, performatic and small (~1.5kb).
let left = {
keep: 'keep',
simple: 10,
obj: { a: { multi: { level: 'property' } }, is: 'ok' },
merge: [0, 1, 2, 3],
append: [0, 1, 2],
prepend: [0, 1, 2]
};
let right = {
simple: 20,
obj: { a: { multi: { level: 'and' }, deep: 'property' } },
merge: [10, 20],
append: { $append: [3, 4, 5] },
prepend: { $prepend: [-2, -1] }
};
let result = merge(left, right);
console.log(result);
// Result
{
keep: 'keep',
simple: 20,
obj: { a: { multi: { level: 'and' }, deep: 'property' }, is: 'ok' },
merge: [10, 20, 2, 3],
append: [0, 1, 2, 3, 4, 5],
prepend: [-2, -1, 0, 1, 2]
}
Explanation: it deeply merges right object into left without altering them and their properties. Everything is cloned. Arrays elements are merged based on right parameters (operators) passed as objects.
npm install deepmerge-json
After that you can import it:
import merge from 'deepmerge-json';
or
const merge = require('deepmerge-json');
There is even a Typescript d.ts definition file to support auto complete.
Just add this line to your HTML file:
<script src="https://unpkg.com/deepmerge-json@latest/dist/deepmerge-json.min.js></script>
The main reason this library was created was to mimic and extend some array merging functions from mongodb when merging two sets of properties json files.
It is possible to merge recursively all types of properties.
const left = {
boolValue: false,
numberValue: 100,
stringValue: 'target',
objectValue: {
foo: 0,
bar: 'bar',
baz: {
baz1: 1,
baz2: 2
}
}
};
const right = {
boolValue: true,
numberValue: 222,
stringValue: 'source',
objectValue: {
foo: 'foo',
baz: {
baz3: 3
}
}
};
const res = merge(left, right);
// result
{
boolValue: true,
numberValue: 222,
stringValue: 'source',
objectValue: {
foo: 'foo',
bar: 'bar',
baz: {
baz1: 1,
baz2: 2,
baz3: 3
}
}
}
You can clone an object omitting the second parameter. This will execute the merge function with an empty second parameter, which results in a deep clone of the first one.
Notice that if you pass anything other than undefined to the second parameter (even null), it will be actively used in the merge process.
You can also use the merge.clone() method which is an alias to the merge method with a single parameter. It's also more semantically meaningful.
Merging arrays are special because sometimes you want to append elements, sometimes prepend and sometimes you want to merge them.
Mongodb handles this nicely (IMHO). It has a $push property (among others) that let you append elements to an array when updating a document.
Inspired on that, this library has some merging methods (here called operations) to help you merge or improve the arrays from the original object. Just keep in mind that no matter the depth of the array, you just need to have the same path to the objects you want to merge.
This is the default behavior. It merges the arrays elements one by one. It will add elements to the end if there more on the right than on the left element.
const left = {
foo: [1, 2, 3],
bar: []
};
const right = {
foo: [10, 20],
bar: [10, 20, 30]
};
const result = merge(left, right)
// Result
{
foo: [10, 20, 3],
bar: [10, 20, 30]
}
You can use the $push or $append operation to add elements to the end of the "left" array.
const left = [0, 1, 2];
const right = { $push: [3, 4, 5] };
const result = merge(left, right);
// Result
[0, 1, 2, 3, 4, 5];
Similarly, you can use $prepend operation to add elements to the beginning of the "left" array.
const left = [0, 1, 2];
const right = { $prepend: [-2, -1] };
const result = merge(left, right);
// Result
[-2, -1, 0, 1, 2];
Use $set when you want to completely replace "left" array by the "right" one.
const left = [0, 1, 2, 3, 4, 5, 6];
const right = { $set: [10, 20] };
const result = merge(left, right);
// Result
[10, 20];
Use $replace to replace or add indexed elements by their indexes. Indexes can be numbers or strings and cannot be less than 0 or NaN values.
const left = [10, 20, 30];
const right = { $replace: { 0: 100, 2: 300, 4: 400 } };
const result = merge(left, right);
// Result (note that the element with index 3 was never given)
[100, 20, 300, , 400];
const left = [10, 20, 30];
const right = { $replace: { null: 0, foo: 0, true: 0, '-1': 0 } };
const result = merge(left, right);
// throws an Error
[1.4.0] It completely replaces the indicated left element with the corresponding right element.
Note for users of version
< 1.4.0: if you want the old operation functionality, replace$replacefor$merge.
const left = [{ a: 1, b: 1 }, { c: 1 }];
const right = { $merge: [{ a: 2 }] };
const result = merge(left, right);
// Result
[{ a: 2 }, { c: 1 }];
Use $merge to merge or add indexed elements by their indexes. Indexes can be numbers or strings and cannot be less than 0 or NaN values. It's similar to $replace but instead of replacing the values when found, it merges them with the new values.
const left = [10, 20, 30];
const right = { $merge: { 0: 100, 2: 300, 4: 400 } };
const result = merge(left, right);
// Result (note that the element with index 3 was never given)
[100, 20, 300, , 400];
const left = [10, 20, 30];
const right = { $merge: { null: 0, foo: 0, true: 0, '-1': 0 } };
const result = merge(left, right);
// throws an Error
const left = [{ a: 1, b: 1 }, { c: 1 }];
const right = { $merge: [{ a: 2 }] };
const result = merge(left, right);
// Result
[{ a: 2, b: 1 }, { c: 1 }];
Use $insert to insert indexed elements at their indexes. Indexes can be numbers or strings and cannot NaN values. Notice that elements change places as you insert them. Negative numbers insert them to the end of the array. See Array.splice.
const left = [10, 20, 30];
const right = { $insert: { 0: 100, 2: 200, 10: 400 } };
const result = merge(left, right);
// Result (notice that the elements moved and the 400 was added to the last index)
[100, 10, 200, 20, 30, 400];
const left = [10, 20, 30];
const right = { $insert: { '-1': 100, '-2': 200, '-10': 0 } };
const result = merge(left, right);
// Result
[0, 10, 20, 200, 100, 30];
const left = [10, 20, 30];
const right = { $insert: { null: 100, foo: 300, true: 400 } };
const result = merge(left, right);
// throws an Error
If you skip some elements in the "right" array, the respective "left" elements will be kept in the result. This is not very useful for json merging since it's ot possible to create a sparse array per se, but it's a nice consequence of the merge method.
const left = [1, 20, 3, 40, 5, 60];
const right = [10, , 30, , 50];
const result = merge(left, right);
// Result
[10, 20, 30, 40, 50, 60];
Starting from version 1.3.0 it's possible to use multiple operations at once. They are executed in place and in order.
const left = [2, 3, 4];
const right: {
$prepend: [0, 1],
$append: [5, 6],
$replace: { 0: 100 };
}
const result = merge(left, right);
// Result
[100, 1, 2, 3, 4, 5, 6]
const left = [2, 3, 4];
const right: {
$replace: { 0: 100 };
$prepend: [0, 1],
$append: [5, 6],
}
const result = merge(left, right);
// Result
[0, 1, 100, 3, 4, 5, 6]
You can also merge multiple objects with the help of the utility method merge.multi(). It respects the order of the parameters and the operations just like expected if you call merge multiple times passing the last result as the first parameter to the next call.
const obj1 = { a: 0, b: [true, { c: 'ok' }] };
const obj2 = { a: 10, d: false };
const obj3 = { a: 20, b: { $push: [42] } };
const result = merge.multi(obj1, obj2, obj3);
// Result
{ a: 20, b: [true, { c: 'ok' }, 42], d: false }
For now, no options yet :chipmunk:.
If you are nice enough you can submit bugs and features to the issue board and make this lib great and useful for you and the community.
But if you are really nice you can submit a PR and make this lib awesome!
Just a fun performance test with a 1 million runs. I'm not a performance expert so they might not be very precise.
Testing machine:
| Measures | Node 17.7.2 | Chrome 100.0.4896.75 | Firefox 99.0 2 :thinking: |
|---|---|---|---|
| Max. Value | 279,763.93 | 295,386.07 | 852,514.92 |
| Min. Value | 277,344.35 | 287,802.91 | 827,814.57 |
| Average1 | 279,574.05 | 293,929.66 | 840,884.13 |
[1.5.0] - 2022-02-08
merge operation. It should be used instead of $replace. It works like $replace was before 1.4.0. It merges objects when the index is found and add them when the index is missing.--
FAQs
A library to deep merge json files with array operations
We found that deepmerge-json demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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