Use extends for inheritance.

// bad
const inherits = require('inherits');
function PeekableQueue(contents) {
  Queue.apply(this, contents);
}
inherits(PeekableQueue, Queue);
PeekableQueue.prototype.peek = function () {
  return this.queue[0];
};
// good
class PeekableQueue extends Queue {
    return this.queue[0];
}

9.3 Methods can return this to help with method chaining.

It’s okay to write a custom toString() method, just make sure it works successfully and causes no side effects.

class Jedi {
  constructor(options = {}) {
    this.name = options.name || 'no name';
  }
  getName() {
    return this.name;
  }
  toString() {
    return `Jedi - ${this.getName()}`;

9.5 Classes have a default constructor if one is not specified. An empty constructor function or one that just delegates to a parent class is unnecessary. eslint:

Avoid duplicate class members. eslint: no-dupe-class-members

Why? Duplicate class member declarations will silently prefer the last one - having duplicates is almost certainly a bug.

// bad
class Foo {
  bar() { return 1; }
  bar() { return 2; }
}
// good
class Foo {
  bar() { return 1; }
}
// good
class Foo {
}