npm start

Runs the app in the development mode.
Open http://localhost:3000 to view it in your browser.

Note if there are CORS errors in the console while sending requests, try opening browser with disabled web security Here's how to do it on Mac and Windows:

Mac For Google Chrome:

Close any running instance of Chrome. Run the following command in Terminal:

open -n -a /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --args --user-data-dir="/tmp/chrome_dev_test" --disable-web-security

Windows For Google Chrome:

Close any running instance of Chrome. Press Win + R and run the following command:

chrome.exe --user-data-dir="C:/Chrome dev session" --disable-web-security

Remember to replace chrome.exe with the full path to your Chrome application if it's not added to your PATH.