Mutates an object hash into an object of getters and setters where the setters - if used - will throw an error.

immutabilly.js

function immutabilly(props) {
  Object.keys(props).forEach(key => {
    const prop = props[key];
    if (prop === Object(prop)) {
      immutabilly(prop);
    }
    Object.defineProperty(props, key, {
      enumerable: true,
      get: () => prop,
      set: () => {throw new Error(`Illegal assignment to immutable property '${key}'`);},
    });
  });
  return props;
}