Across the internet that has always been many code playgrounds, places we can practice basic coding drills. Nowadays we have even more robus online coding tools that allow us to even build whole applications online. This is meant to be a list of such tools.
Probably the most well known allowing you to spin an environment for most every language you can think of and many you weren't aware. Considering learning a new language and didn't want to install another IDE and langauge on your machine just yet, Repl.it has your back!
NodeJS prototyping, create APIs and Web Servers then deploy, download the code etc. Have access to the world of node in the browser.
A node coding playground that saves and loads directly into your github gists.
Create automations, apis and deploy them online with this online code editor.
Another online code editor for web based applications similar to CodePen.io.
Online full featured IDE for working in projects in several languages.
An online community to develop, deploy nodeJS applications as a community. Lots of templates for popular frameworks and APIs.
Focuses on python exclusively, allows you to host, develop and deploy applications and databases from their platform.
There are many JS coding sandboxes/pastbins such as