ts_temp/array/indexBy.js
import curryN from '../function/curryN';
/**
* Given a function that generates a key, turns a list of objects into an
* object indexing the objects by the given key. Note that if multiple
* objects generate the same value for the indexing key only the last value
* will be included in the generated object.
*
* @param {Function} fn Function :: a -> String
* @param {Array} arr The array of objects to index
* @return {Object} An object indexing each array element by the given property.
* @example
*
* var list = [{id: 'xyz', title: 'A'}, {id: 'abc', title: 'B'}];
* indexBy(x => x.id, list);
* //=> {abc: {id: 'abc', title: 'B'}, xyz: {id: 'xyz', title: 'A'}}
*/
export default curryN(2, (fn, arr = []) => {
const result = {};
for (let i = 0; i < arr.length; i++) {
result[fn(arr[i], i, arr)] = arr[i];
}
return result;
});