@dillonkearns/elm-graphql
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Flow
/**
* Copyright (c) 2015-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow
*/
import type {ObjMap} from './ObjMap';
/**
* Creates a keyed JS object from an array, given a function to produce the keys
* and a function to produce the values from each item in the array.
*
* const phoneBook = [
* { name: 'Jon', num: '555-1234' },
* { name: 'Jenny', num: '867-5309' }
* ]
*
* // { Jon: '555-1234', Jenny: '867-5309' }
* const phonesByName = keyValMap(
* phoneBook,
* entry => entry.name,
* entry => entry.num
* )
*
*/
export default function keyValMap<T, V>(
list: Array<T>,
keyFn: (item: T) => string,
valFn: (item: T) => V
): ObjMap<V> {
return list.reduce(
(map, item) => ((map[keyFn(item)] = valFn(item)), map),
Object.create(null)
);
}