var express = require('express');
var app = express();

var actions = new Map();
actions.put("play", function play(data) {
    // ...
});
actions.put("pause", function pause(data) {
    // ...
});

app.get('/perform/:action/:payload', function(req, res) {
    let action = actions.get(req.params.action); // $ Source
    res.end(action(req.params.payload)); // $ Alert
});