Custom Elements

ES5 + __proto__

// And in browsers that support __proto__:

document.register('x-foo', {
  extends: 'p',
  prototype: {
    __proto__: HTMLParagraphElement.prototype,
    get foo() { return 'foo'; }
  }
})

ES5 assign.js

var p = Object.create(HTMLParagraphElement.prototype);
p.hello = function() { alert('world'); };

document.register('x-foo', {
  extends: 'p',
  prototype: p
})

ES5-proto.js

// And in browsers that support __proto__:

document.register('x-foo', {
  extends: 'p',
  prototype: {
    __proto__: HTMLParagraphElement.prototype,
    get foo() { return 'foo'; }
  }
})

ES5-standard.js

document.register('x-foo', {
  extends: 'p',
  prototype: Object.create(HTMLParagraphElement.prototype, {
    foo: {
      get: function() { return foo; },
      enumerable: true,
      configurable: true
    }
  })
})