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https://github.com/arve0/deep-reduce
reduce objects deeply, call reducer for every nested value in object tree
https://github.com/arve0/deep-reduce
array deeply-nested nested-values object reduce values
Last synced: 8 days ago
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reduce objects deeply, call reducer for every nested value in object tree
- Host: GitHub
- URL: https://github.com/arve0/deep-reduce
- Owner: arve0
- License: mit
- Created: 2017-06-12T18:36:55.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2017-10-10T05:49:18.000Z (about 7 years ago)
- Last Synced: 2024-11-07T06:20:30.494Z (13 days ago)
- Topics: array, deeply-nested, nested-values, object, reduce, values
- Language: JavaScript
- Homepage:
- Size: 25.4 KB
- Stars: 3
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
[](https://travis-ci.org/arve0/deep-reduce) [](https://badge.fury.io/js/deep-reduce)
# deep-reduce
Reduce objects deeply, call reducer for every nested node in object tree. Use `deepReduce` for
transforming/getting values from awfully nested objects. `deepReduce` also traverse arrays.
## Install
```sh
npm i deep-reduce
```
## Usage
[Try example in browser](https://runkit.com/npm/deep-reduce).
```js
const deepReduce = require('deep-reduce')
const deepEqual = require('assert').deepEqual
// let nested leaf values be equal to their path, for demonstration purpose
let deepNestedObject = {
a: 'a',
b: { c: 'b.c' },
c: [
'c.0',
{
d: 'c.1.d',
e: [
'c.1.e.0'
]
}
]
}
// store all values which are strings to reduced[path].
let flattenStrings = (reduced, value, path) => {
if (typeof value === 'string') {
reduced[path] = value
}
return reduced
}
// the reduced value is returned
let reduced = deepReduce(deepNestedObject, flattenStrings)
// we should now have this object
deepEqual(reduced, {
'a': 'a',
'b.c': 'b.c',
'c.0': 'c.0',
'c.1.d': 'c.1.d',
'c.1.e.0': 'c.1.e.0'
})
```
Root object may be an array also:
```js
deepReduce([{a: 1},{b: 2},{a: 3}], (r,v) => typeof v === 'number' ? r + v : r, 0)
// 6
```
Here is how you would collect all items of nested arrays at some specific path:
```js
// we want to get contents from all packets
let transport = {
id: 'A8811',
packages: [
{
id: 'P100',
contents: [
{
id: 'R88',
name: 'resistor'
},
{
id: 'C99',
name: 'capacitor'
}
]
}, {
id: 'P101',
contents: [
{
id: 'C96',
name: 'coil'
}
]
}
]
}
let contents = deepReduce(transport, (reduced, value, path) => {
if (path.match(/packages\.\d+\.contents\.\d+$/)) {
// path is packages.n.contents.m
// item n in packages array
// item m in contents array
reduced.push(value)
}
return reduced
}, []) // start with an empty array
// [ { id: 'R88', name: 'resistor' },
// { id: 'C99', name: 'capacitor' },
// { id: 'C96', name: 'coil' } ]
```
## API
`deepReduce` takes 5 arguments. 2 mandatory and 3 optional:
```ts
deepReduce (
obj: object,
reducer: (reduced: any, value: any, path: string, root: object) => any,
reduced = {},
path = '',
thisArg = {}): any
```
### Arguments
- `obj` Object to traverse.
- `reducer` Function to call with every value in `obj`-tree. See section below
for [`reducer` function signature](#arguments-for-reducer-function).
- `reduced` Initial value of `reduced` passed to `reducer`. Defaults to empty object `{}`.
- `path` Path to root, start traversing here. Nice to omit looping through parts of `obj`.
Example:
```js
deepReduce({ a: [1,2,3], b: { c: [3, 3] } }, (reduced, val) => reduced + val, 1, 'b.c')
// only traverses b.c, returns 1 + 3 + 3 = 7
```
- `thisArg` Bound to reducer as `this`.
### Arguments for reducer function
The reducer function is called with these arguments:
```ts
(reduced: any, value: any, path: string, root: object) => any
```
- `reduced` Initial or current reduced value.
- `value` Value of current node.
- `path` Path to current value.
- `root` Root object passed to `deepReduce` as `obj`.
The `reducer` should return the `reduced` value.
## Performance
`deep-reduce` traverses every node of a 149 kb JSON in 10 milliseconds on a macbook air 2013 i5 1.3GHz, see [test.js](test.js#L68-L73).
You can omit traversal of parts of the object tree with defining a start `path`:
```js
deepReduce(object, reducer, initialValue, 'start.at.this.path')
```
...which may give some performance gains.
If you want to use this client size, bundle size is ~ 387 B, 209 B gzipped.
## Development
```sh
git clone https://github.com/arve0/deep-reduce
cd deep-reduce
npm start # watches index.ts and builds on any change
npm test # runs node test.js
```
## License
MIT © 2017 Arve Seljebu