Properly inheriting objects in Javasacript

_usage.js

function Child() {
    Parent.call(this);
}

extends(Child, Parent);

coffee.js

function extend(child, parent) {
  for (var key in parent) {
    if (Object.hasOwnProperty.call(parent, key)) {
      child[key] = parent[key];
    }
  }
  function ctor() {
    this.constructor = child;
  }
  ctor.prototype = parent.prototype;
  child.prototype = new ctor;
  child.super_ = parent.prototype;
};

mdn.js

function extend(child, parent) {
  child.prototype = Object.create(parent.prototype);
  child.prototype.constructor = parent;
}

node.js

function extend(child, parent) {
  child.super_ = parent;
  child.prototype = Object.create(parent.prototype, {
    constructor: {
      value: child,
      enumerable: false,
      writable: true,
      configurable: true
    }
  });
};