mergeWithKey.js•1.38 kB
var _curry3 = require('./internal/_curry3');
var _has = require('./internal/_has');
/**
* Creates a new object with the own properties of the two provided objects. If
* a key exists in both objects, the provided function is applied to the key
* and the values associated with the key in each object, with the result being
* used as the value associated with the key in the returned object. The key
* will be excluded from the returned object if the resulting value is
* `undefined`.
*
* @func
* @memberOf R
* @since v0.19.0
* @category Object
* @sig (String -> a -> a -> a) -> {a} -> {a} -> {a}
* @param {Function} fn
* @param {Object} l
* @param {Object} r
* @return {Object}
* @see R.merge, R.mergeWith
* @example
*
* let concatValues = (k, l, r) => k == 'values' ? R.concat(l, r) : r
* R.mergeWithKey(concatValues,
* { a: true, thing: 'foo', values: [10, 20] },
* { b: true, thing: 'bar', values: [15, 35] });
* //=> { a: true, b: true, thing: 'bar', values: [10, 20, 15, 35] }
*/
module.exports = _curry3(function mergeWithKey(fn, l, r) {
var result = {};
var k;
for (k in l) {
if (_has(k, l)) {
result[k] = _has(k, r) ? fn(k, l[k], r[k]) : l[k];
}
}
for (k in r) {
if (_has(k, r) && !(_has(k, result))) {
result[k] = r[k];
}
}
return result;
});