summaryrefslogtreecommitdiff
path: root/school/node_modules/graphql/jsutils/promiseReduce.js.flow
diff options
context:
space:
mode:
Diffstat (limited to 'school/node_modules/graphql/jsutils/promiseReduce.js.flow')
-rw-r--r--school/node_modules/graphql/jsutils/promiseReduce.js.flow25
1 files changed, 25 insertions, 0 deletions
diff --git a/school/node_modules/graphql/jsutils/promiseReduce.js.flow b/school/node_modules/graphql/jsutils/promiseReduce.js.flow
new file mode 100644
index 0000000..ea333bc
--- /dev/null
+++ b/school/node_modules/graphql/jsutils/promiseReduce.js.flow
@@ -0,0 +1,25 @@
+// @flow strict
+import type { PromiseOrValue } from './PromiseOrValue';
+
+import isPromise from './isPromise';
+
+/**
+ * Similar to Array.prototype.reduce(), however the reducing callback may return
+ * a Promise, in which case reduction will continue after each promise resolves.
+ *
+ * If the callback does not return a Promise, then this function will also not
+ * return a Promise.
+ */
+export default function promiseReduce<T, U>(
+ values: $ReadOnlyArray<T>,
+ callback: (U, T) => PromiseOrValue<U>,
+ initialValue: PromiseOrValue<U>,
+): PromiseOrValue<U> {
+ return values.reduce(
+ (previous, value) =>
+ isPromise(previous)
+ ? previous.then((resolved) => callback(resolved, value))
+ : callback(previous, value),
+ initialValue,
+ );
+}