A alternate approach to write a switch statement that supports composability and reusability.

switch-delegator.js

// Example returns for illustration only.
const cases = {
  alpha() {
    return [ "Alpha", arguments.length ];
  },
  beta() {
    return [ "Beta", arguments.length ];
  },
  _default() {
    return [ "Default", arguments.length ];
  }
};
 
const delegator = (key, ...args) => {
  const delegate = cases.hasOwnProperty(key)
    ? cases[key]      // Derive the method to delegate operation to
    : cases._default; // Assign the default case handler
 
  // The scope arg could be set to something specific,
  // in this case, null will suffice
  return delegate.apply(null, args);
};
 
// Put the API to work:
delegator( "alpha", 1, 2, 3, 4, 5 );
  //=> [ "Alpha", 5 ]