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copy-props

Copy properties between two objects deeply.

Install

To install from npm:

$ npm i copy-props --save

Load this module

For Node.js:

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

For Web browser:

<script src="copy-props.min.js"></script>

Usage

Copy src to dst simply (and return dst) :

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) :

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) :

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 :

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):

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' }

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.

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.

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.
```
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

This program is free software under MIT License. See the file LICENSE in this distribution for more details.

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