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 defun. Try it out:
const defun = require('defun').defun;
const sum = defun({
'[]':0,
'(x:xs)':(x,xs)=>x+sum(xs)
});
sum([1,2,3,4,5])
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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
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