Immutable object factory, using proxies

immutable-proxy-example.js

const immutable = require('./immutable');
let obj;

obj = immutable({ foo: 'bar' });
obj.foo = 'baz';      // assignment fails silently
delete obj.foo;       // delete fails silently

obj = immutable({ foo: [ 1, 2, 3 ] });
obj.foo.push( 4 );    // mutation fails silently

obj = immutable({ foo: { bar: true } });
obj.foo.bar = false;  // deep assignment fails silently

immutable.js

'use strict';

function isObject( arg ) {
  const t = typeof arg;
  return ( t === 'object' || t === 'function' ) && arg !== null;
}

const immutableHandler = {

  get( target, prop ) {
    const val = Reflect.get( target, prop );
    if ( isObject( val ) ) {
      return new Proxy( val, immutableHandler );
    }
    return val;
  },

  set() {
    return true;
  },

  deleteProperty() {
    return true;
  }

};

module.exports = val => new Proxy( val, immutableHandler );