From 607a6d426d36499ce268ce9b5bba12ec2436d402 Mon Sep 17 00:00:00 2001
From: William Chargin <wchargin@gmail.com>
Date: Tue, 13 Aug 2019 09:20:54 -0700
Subject: [PATCH] Fix type error in FileUploader (#1280)

Summary:
Introduced in #1277.

Test Plan:
Run `yarn start` and visit <http://localhost:8080/test/FileUploader/>.
Conduct the test plan as specified on that page.

wchargin-branch: fileuploader-target
---
 src/util/FileUploader.js | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/util/FileUploader.js b/src/util/FileUploader.js
index c0ca96b..90050ec 100644
--- a/src/util/FileUploader.js
+++ b/src/util/FileUploader.js
@@ -24,8 +24,11 @@ export class FileUploader extends React.Component<Props> {
     const onUpload = (e) => {
       const file = e.target.files[0];
       const reader = new FileReader();
-      reader.onload = (e) => {
-        const jsonString = e.target.result;
+      reader.onload = () => {
+        const jsonString = reader.result;
+        if (typeof jsonString !== "string") {
+          throw new Error("Unexpected: jsonString is not string");
+        }
         const json = JSON.parse(jsonString);
         this.props.onUpload(json);
       };