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+// @flow strict
+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: $ReadOnlyArray<T>,
+ keyFn: (item: T) => string,
+ valFn: (item: T) => V,
+): ObjMap<V> {
+ return list.reduce((map, item) => {
+ map[keyFn(item)] = valFn(item);
+ return map;
+ }, Object.create(null));
+}