Copy properties deeply between two objects
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README.md

copy-props NPM MIT License Build Status Build Status Coverage Status

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

Copyright (C) 2016-2018 Takayuki Sato

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