copy-props

Copy properties deeply between two objects.

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copy-props
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Copy properties between two objects deeply.

Install

To install from npm:
$ npm i copy-props --save

Usage

Copy src to dst simply (and return dst) :
const copyProps = require('copy-props');

var src = { a: 1, b: { b1: 'bbb' }, c: 'ccc' };
var dst = { a: 2, b: { b1: 'xxx', b2: 'yyy' } };

copyProps(src, dst);
// => { a: 1, b: { b1: 'bbb', b2: 'yyy' }, c: 'ccc' }

Copy src to dst with property mapping (and return dst) :
const copyProps = require('copy-props');

var src = { a: 1, b: { b1: 'bbb' }, c: 'ccc', d: 'ddd' };
var dst = { f: { a: 2, b1: 'xxx', b2: 'yyy' }, e: 'zzz' };

copyProps(src, dst, {
  a: 'f.a',
  'b.b1': 'f.b1',
  'b.b2': 'f.b2',
  c: 'f.c',
});
// => { f: { a: 1, b1: 'bbb', b2: 'yyy', c: 'ccc' }, e: 'zzz' }

Copy src to dst with convert function (and return dst) :
const copyProps = require('copy-props');

var src = { a: 1, b: { b1: 'bbb' } };
var dst = { a: 0 };

copyProps(src, dst, function (srcInfo) {
  if (srcInfo.keyChain === 'a') {
    return srcInfo.value * 2;
  }
  if (srcInfo.keyChain === 'b.b1') {
    return srcInfo.value.toUpperCase();
  }
});
// => { a: 2, b: { b1: 'BBB' } }

Can use an array instead of a map as property mapping :
const copyProps = require('copy-props');

var src = { a: 1, b: { c: 'CCC' }, d: { e: 'EEE' } };
var dst = { a: 9, b: { c: 'xxx' }, d: { e: 'yyy' } };
var fromto = ['b.c', 'd.e'];
copyProps(src, dst, fromto);
// => { a: 9, b: { c: 'CCC' }, d: { e: 'EEE' } }

Can copy reversively (from dst to src) by reverse flag (and return src):
const copyProps = require('copy-props');

var src = { a: 1, b: { b1: 'bbb' }, c: 'ccc' };
var dst = { a: 2, b: { b1: 'xxx', b2: 'yyy' } };

copyProps(src, dst, true);
// => { a: 2, b: { b1: 'xxx', b2: 'yyy' }, c: 'ccc' }

const copyProps = require('copy-props');

var src = { a: 1, b: { b1: 'bbb' }, c: 'ccc', d: 'ddd' };
var dst = { f: { a: 2, b1: 'xxx', b2: 'yyy' }, e: 'zzz' };

copyProps(
  src,
  dst,
  {
    a: 'f.a',
    'b.b2': 'f.b2',
    c: 'f.c',
  },
  true
);
// => { a: 2, b: { b1: 'bbb', b2: 'yyy' }, c: 'ccc', d: 'ddd' }

If a value of source property is undefined (when not using converter), or a result of converter is undefined (when using converter), the value is not copied.
const copyProps = require('copy-props');

var src = { a: 'A', b: undefined, c: null, d: 1 };
var dst = { a: 'a', b: 'b', c: 'c' };

copyProps(src, dst, function (srcInfo) {
  if (srcInfo.keyChain === 'd') {
    return undefined;
  } else {
    return srcInfo.value;
  }
});
// => { a: 'A', b: 'b', c: null }

You can operate the parent node object directly in converter.
const copyProps = require('copy-props');

var src = { a: 1, b: 2 };
var dst = {};

copyProps(src, dst, function (srcInfo, dstInfo) {
  Object.defineProperty(dstInfo.parent, dstInfo.key, {
    writable: false,
    enumerable: true,
    configurable: false,
    value: srcInfo.value * 2,
  });
}); // => { a: 2, b: 4 }

dst; // => { a: 2, b: 4 }
dst.a = 9;
dst; // -> { a: 2, b: 4 }

API

copyProps(src, dst , fromto , converter , reverse) => object

Copy properties of src to dst deeply. If fromto is given, it is able to copy between different properties. If converter is given, it is able to convert the terminal values.

Parameters:

| Parameter | Type | Description | | :---------- | :-----------------: | :------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | src | object | A source object of copy. | | dst | object | A destinate object of copy. | | fromto | object | array | An object mapping properties between src and dst. (Optional) | | converter | function | A function to convert terminal values in src. (Optional) | | reverse | boolean | True, if copying reversively from dst to src and returns src object. fromto is also reversively used from value to key. This default value is false. (Optional) |

Returns:

dst object after copying.
Type: object
  • Format of fromto

fromto is a non-nested key-value object. And the keys are property key chains of src and the values are property key chains of dst. The key chain is a string which is concatenated property keys on each level with dots, like 'aaa.bbb.ccc'.
The following example copys the value of src.aaa.bbb.ccc to dst.xxx.yyy.
```js copyProps(src, dst, {
'aaa.bbb.ccc': 'xxx.yyy',
}); ```
fromto can be an array. In that case, the array works as a map which has pairs of same key and value.
  • API of converter

converter(srcInfo, dstInfo) : Any
converter is a function to convert terminal values of propeerties of src.
Parameters:
| Parameter | Type | Description | | :-------- | :----: | :---------------------------------------------------------------- | | srcInfo | object | An object which has informations about the current node of src. | | dstInfo | object | An object which has informations about the current node of dst. |
Return:
The converted value to be set as a destination property value. If this value is undefined, the destination property is not set to the destination node object.
Type: Any
- Properties of srcInfo and dstInfo
_srcInfo_ and _dstInfo_ has same properties, as follows:

| Property   |  Type  | Description                                             |
| :--------- | :----: | :------------------------------------------------------ |
| _value_    | _Any_  | The value of the current node.                          |
| _key_      | string | The key name of the current node.                       |
| _keyChain_ | string | The full key of the current node concatenated with dot. |
| _depth_    | number | The depth of the current node.                          |
| _parent_   | object | The parent node of the current node.                    |

License

MIT