THRIFT-4551: Add Prettier for consistent JS code formatting (#1536)

Client: js
diff --git a/package-lock.json b/package-lock.json
index 27bd5e9..4b16899 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1382,6 +1382,12 @@
       "integrity": "sha1-IZMqVJ9eUv/ZqCf1cOBL5iqX2lQ=",
       "dev": true
     },
+    "prettier": {
+      "version": "1.11.1",
+      "resolved": "https://unpm.uberinternal.com/prettier/-/prettier-1.11.1.tgz",
+      "integrity": "sha512-T/KD65Ot0PB97xTrG8afQ46x3oiVhnfGjGESSI9NWYcG92+OUPZKkwHqGWXH2t9jK1crnQjubECW0FuOth+hxw==",
+      "dev": true
+    },
     "process-nextick-args": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/process-nextick-args/-/process-nextick-args-2.0.0.tgz",
diff --git a/package.json b/package.json
index b03fc57..47bce67 100644
--- a/package.json
+++ b/package.json
@@ -46,11 +46,13 @@
     "istanbul": "^0.4.5",
     "jsdoc": "^3.5.5",
     "phantomjs-prebuilt": "^2.1.16",
+    "prettier": "1.11.1",
     "tape": "^4.9.0",
     "utf-8-validate": "^4.0.0"
   },
   "scripts": {
     "cover": "lib/nodejs/test/testAll.sh COVER",
-    "test": "lib/nodejs/test/testAll.sh"
+    "test": "lib/nodejs/test/testAll.sh",
+    "prettier": "prettier --write '**/*.js'"
   }
 }