https://github.com/peternaydenov/walk
Deep copy with fine control during the process. Can be used also as a deep 'forEach'
https://github.com/peternaydenov/walk
callback deep-copy object-callback property-callback
Last synced: about 1 month ago
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Deep copy with fine control during the process. Can be used also as a deep 'forEach'
- Host: GitHub
- URL: https://github.com/peternaydenov/walk
- Owner: PeterNaydenov
- License: mit
- Created: 2022-03-04T06:11:17.000Z (about 3 years ago)
- Default Branch: master
- Last Pushed: 2025-04-28T07:11:28.000Z (about 1 month ago)
- Last Synced: 2025-04-28T08:25:42.236Z (about 1 month ago)
- Topics: callback, deep-copy, object-callback, property-callback
- Language: JavaScript
- Homepage:
- Size: 187 KB
- Stars: 3
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: Changelog.md
- License: LICENSE
Awesome Lists containing this project
README
# Walk (@peter.naydenov/walk) ( Version 5.x.x )
Creates an immutable copies of javascript data structures(objects, arrays or mixed). Executes callback functions on every object property(object-callback) and every primitive property(key-callback). Callbacks can modify result-object during the walk process. Mask, filter or substitute values during the copy process.
```js
const result = walk ({
data // (required) Any JS data structure;
, objectCallback // (optional) Function executed on each object property;
, keyCallback // (optional) Function executed on each primitive property;
})
// Result will become a exact deep copy of "data"
// - if callbacks are not defined
// - if callbacks are resolved with "value" without modification
```
## keyCallback
function "**keyCallback**" of the `walk` could be used also as a deep '**forEach**' method no matter of the type of the object(object or array). KeyCallback will be executed on keys that have value type: *string, number, bigint, boolean, symbol, null, undefined, and function*.
Object and arrays will be executed only in objectCallback.
```js
function keyCallbackFn ({value,key,breadcrumbs, IGNORE }) {
// value: value for the property;
// key: key of the property;
// breadcrumbs: location of the property;
// IGNORE: constant. Return it if key-value pair should be ignored;
// Callback should return the value of the property. To ignore property, return constant argument IGNORE
}
let result = walk ({ data, keyCallback: keyCallbackFn }); // It's the short way to provide only key-callback. Callback functions are optional.
// let result = walk ({ data, keyCallback, objectCallback }); // If both callbacks are available
```
## objectCallback
Optional callback function that is started on each object property including 'root'. Function should return object or will be ignored in copy process.
```js
function objectCallbackFn ({ value, key, breadcrumbs, IGNORE }) {
// value: each object during the walk
// key: key of the object
// breadcrumbs: location of the object
// IGNORE: Constant. Return it if key-value pair should be ignored;
// object callback should return something.
}
let result = walk ({ data, keyCallback:keyCallbackFn, objectCallback : objectCallbackFn })
```
**IMPORTANT: Object-callbacks are executed always before key-callbacks. If we have both callbacks, then key-callbacks will be executed on the result of object-callback.**
Skip key-callbacks by not defining them:
```js
let result = walk ({ data, objectCallback: objectCallbackFn }) // ignore keyCallback
```
## Installation
Install for node.js projects by writing in your terminal:
```
npm install @peter.naydenov/walk
```
Once it has been installed, it can be used by writing this line of JavaScript:
```js
import walk from '@peter.naydenov/walk'
```
## How to use it
### Deep copy
```js
let myCopy = walk ({ data:x }) // where x is some javascript data structure
```
### Deep 'forEach'
```js
let x = {
ls : [ 1,2,3 ]
, name : 'Peter'
, props : {
eyeColor: 'blue'
, age : 47
, height : 176
, sizes : [12,33,12,21]
}
};
walk ({ data:x, keyCallback : ({value,key, breadcrumbs}) => {
console.log (`${key} ----> ${value}`) // Show each each primitive couples key->value
console.log ( `Property location >> ${breadcrumbs}`)
// example for breadcrumbs: 'age' will looks like this : 'root/props/age'
}
})
```
### Ignore a key
```js
let x = {
ls : [ 1,2,3 ]
, name : 'Peter'
, props : {
eyeColor: 'blue'
, age : 47
, height : 176
, sizes : [12,33,12,21]
}
};
let result = walk ({ data:x, keyCallback : ({ value, key, IGNORE }) => {
if ( key === 'name' ) return IGNORE
return value
})
// result will copy all properties from x without the property 'name'.
// result.name === undefined
```
### Mask values
```js
let x = {
ls : [ 1,2,3 ]
, name : 'Peter'
, props : {
eyeColor: 'blue'
, age : 47
, height : 176
, sizes : [12,33,12,21]
}
};
let result = walk ({ data:x, keyCallback : () => 'xxx' })
// 'result' will have the same structure as 'x' but all values are 'xxx'
// {
// ls : [ 'xxx','xxx','xxx' ]
// , name : 'xxx'
// , props : {
// eyeColor: 'xxx'
// , age : 'xxx'
// , height : 'xxx'
// , sizes : ['xxx','xxx','xxx','xxx']
// }
// }
```
### Change object on condition
```js
let x = {
ls : [ 1,2,3 ]
, name : 'Peter'
, props : {
eyeColor: 'blue'
, age : 48
, height : 176
, sizes : [12,33,12,21]
}
};
function objectCallback ({ value:obj, key, breadcrumbs }) {
if ( key === 'root' ) return obj // Add this row to ignore 'root' object
const {age, height} = obj;
if ( age && age > 30 ) {
return { age, height }
}
return obj
}
let result = walk ({ data:x, objectCallback })
// 'result.props' will have only 'age' and 'height' properties.
// {
// ls : [ 1,2,3 ]
// , name : 'Peter'
// , props : {
// age : 48
// , height : 176
// }
// }
```
## Limitations
- `walk` keyCallback can return only primitives;
- `walk` can not execute another `walk` from inside of the callbacks;
- It's not recomended to use any async operations in the callbacks. Could compromise the result without any warning;
These limitations are covered in a bit larger library - [walk-async](https://github.com/PeterNaydenov/walk-async). Interface is very simular but result is coming as a promise and callbacks should be resolved or rejected.
## Links
- [Release history](Changelog.md)
- [ Walk-async library](https://github.com/PeterNaydenov/walk-async)
- [ Documentation version 4.x.x](https://github.com/PeterNaydenov/walk/blob/master/README_v.4.x.x.md)
- [ Migration guide ](https://github.com/PeterNaydenov/walk/blob/master/Migration.guide.md)
## Credits
'@peter.naydenov/walk' was created and supported by Peter Naydenov.
## License
'@peter.naydenov/walk' is released under the MIT License.