Inheritance problems on ES2015 with properties before 'super'.

es6-classes.js

class View {
  constructor() {
    // require tagName and className to create element
  }
}

class Input extends View {
  constructor(...args) {
    this.tagName = 'input';
    this.className = 'form-control input';
    super(...args);
  }
}

class TextArea extends Input {
  constructor(...args) {
    this.tagName = 'textarea';
    this.className = 'form-control textarea';
    super(...args);
  }
}


console.log('create new Input');
var input = new Input();
console.assert(input.tagName === 'input'); //ok 
console.assert(input.className = 'form-control input'); // ok

console.log('create new TextArea');
var textarea = new TextArea();
console.assert(textarea.tagName === 'textarea'); // fail
console.assert(textarea.className === 'form-control textarea'); // fail

simplest.js

// Simplest example
class A {
  x = 5;
}

class B extends A {
  x = 0;
}

let b = new B();

console.log(b.x); // 5

Link to traceur playground with this code