copy-props

Copy properties deeply between two objects.

Install

$ npm i copy-props

Usage

• Load this module :

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

• 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.b.b1',
    'b.b2': 'f.b.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(value, keyChain) {
    if (keyChain === 'a') {
      return value * 2;
    }
    if (keyChain === 'b.b1') {
      return value.toUpperCase();
    }
  });
  // => { a: 2, b: { b1: 'BBB' } }

API

copyProps(src, dst [, fromToProps] [, converter]) => object

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

• Arguments:

  • src [object] : a source object of copy.
  • dst [object] : a destinate object of copy.
  • fromToProps [object] : an object mapping properties between src and dst.
  • converter [function] : a function to convert terminal values in src.

• Return [object] : dst object after copying.

Format of fromToProps

fromToProps 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'
})

API of converter

converter(value, keyChain) => any

converter is a function to convert terminal values of propeerties of src.

• Arguments:

  • value [any] : a property value to be converted.
  • keyChain [string] : a string of property keys concatenated with dots.

• Return: [any] : converted value.

License

MIT