| /** |
| * 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. |
| * ```ts |
| * const phoneBook = [ |
| * { name: 'Jon', num: '555-1234' }, |
| * { name: 'Jenny', num: '867-5309' } |
| * ] |
| * |
| * const entriesByName = keyMap( |
| * phoneBook, |
| * entry => entry.name |
| * ) |
| * |
| * // { |
| * // Jon: { name: 'Jon', num: '555-1234' }, |
| * // Jenny: { name: 'Jenny', num: '867-5309' } |
| * // } |
| * |
| * const jennyEntry = entriesByName['Jenny'] |
| * |
| * // { name: 'Jenny', num: '857-6309' } |
| * ``` |
| */ |
| export function keyMap(list, keyFn) { |
| const result = Object.create(null); |
| |
| for (const item of list) { |
| result[keyFn(item)] = item; |
| } |
| |
| return result; |
| } |