| /** |
| * Creates a keyed JS object from an array, given a function to produce the keys |
| * for each value in the array. |
| * |
| * This provides a convenient lookup for the array items if the key function |
| * produces unique results. |
| * |
| * const phoneBook = [ |
| * { name: 'Jon', num: '555-1234' }, |
| * { name: 'Jenny', num: '867-5309' } |
| * ] |
| * |
| * // { Jon: { name: 'Jon', num: '555-1234' }, |
| * // Jenny: { name: 'Jenny', num: '867-5309' } } |
| * const entriesByName = keyMap( |
| * phoneBook, |
| * entry => entry.name |
| * ) |
| * |
| * // { name: 'Jenny', num: '857-6309' } |
| * const jennyEntry = entriesByName['Jenny'] |
| * |
| */ |
| export default function keyMap(list, keyFn) { |
| return list.reduce(function (map, item) { |
| map[keyFn(item)] = item; |
| return map; |
| }, Object.create(null)); |
| } |