sandbox-svc.js

const express = require('express')
const vm = require('vm')


let app = express()

app.use(function(req, res, next) {
    req.body = ''
    req.setEncoding('utf8');
  
    req.on('data', (chunk) => { 
        req.body += chunk
    })
  
    req.on('end', () => {
        next()
    })
})

app.post('/', (req, res) => {
    if (req.body) {
        let ctx = {}
        try {
            let x = vm.runInNewContext(req.body, ctx)
            ctx['res'] = x || null
            res.send(ctx)
        } catch (ex) {
            res.send('Error')
        }
    }
})

app.listen(3000, () => {
    console.log('Listening on port 3000')
})