RunKit + 
Try any Node.js package right in your browser
This is a playground to test code. It runs a full Node.js environment and already has all of npm’s 1,000,000+ packages pre-installed, including async.constant. Try it out:
var asyncConstant = require("async.constant")
- all documents on RunKit are public
require()any package directly from npm- use arrow functions, classes, template strings, and most of ES6
awaitany promise instead of using callbacks (example)- create your own embedded node.js snippets
This service is provided by RunKit and is not affiliated with npm, Inc or the package authors.