planning

node_modules/graphql/jsutils/keyValMap.js.flow

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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));
+}