Pattern for refable entities

entry.js

/**
 * I represent a domain entity within the
 * system called "entry". I have a $ref
 * property which is a unique identifier
 * that can be used to address me.
 */
class Entry {
  
  constructor(data) {
    this._$ref = EntryRef.from(data.$ref);
    // Other properties
  }
  
  get $ref() {
    return this._$ref;
  }
  
}

/**
 * I represent a reference to an "entry"
 * domain entity within the system. I
 * can be used to indicate which "entry"
 * an operation should be performed on.
 * I am a value object.
 */
class EntryRef {
  
  constructor(value) {
    this._$ref = value;
  }
  
  get $ref() {
    return this._$ref;
  }
  
  toString() {
    return this._$ref;
  }
  
  valueOf() {
    return this._$ref;
  }
  
  static from(value) {
    return value instanceof EntryRef ?
      value : value.$ref instanceof EntryRef ?
        value.$ref : new EntryRef(value.$ref ?
          value.$ref : value);
  }
  
}

function acceptsRefableEntry(refable) {
  var ref = EntryRef.from(refable);
  // Do stuff with ref
}

// All of the following are analogous
acceptsRefableEntry('http://example.com/entries/abc123');
acceptsRefableEntry(new EntryRef('http://example.com/entries/abc123'));
acceptsRefableEntry(new Entry({
  $ref: 'http://example.com/entries/abc123'
}));
acceptsRefableEntry(new Entry({
  $ref: new EntryRef('http://example.com/entries/abc123')
}));
acceptsRefableEntry(new Entry({
  $ref: new Entry({
    $ref: 'http://example.com/entries/abc123'
  })
}));