If the node version is v9, it can not successfully run `npm run start` command

**Describe the bug**
The bug occurs when the node version is v9, and if the node version is v8, it can work as normal.

**To Reproduce**
Steps to reproduce the behavior:
1. `$nvm use v9` switch to the v9 version of Node.js.
2. `$npm install` to install the packages.
3. `$npm run start` to start the development server.
4. It will stuck at the starting condition forever.