Let's suppose that I have the following object function:

function A(options){
 ...
}

Then I want to create a new function (B) that inherits A's prototype. These are the conditions I'm looking for:

• B's prototype, if modified, should not modify A's
• when calling to B function as a constructor, A's constructor should be called with the corresponding options.

B should look like this:

function B(aOptions, bOptions){ ... }

var b = new B({}, {})

Let's suppose that I have the following object function:

function A(options){
 ...
}

Then I want to create a new function (B) that inherits A's prototype. These are the conditions I'm looking for:

• B's prototype, if modified, should not modify A's
• when calling to B function as a constructor, A's constructor should be called with the corresponding options.

B should look like this:

function B(aOptions, bOptions){ ... }

var b = new B({}, {})

• javascript

Share Improve this question Follow edited Oct 10, 2014 at 16:21 Dan D. 74.7k1515 gold badges110110 silver badges127127 bronze badges asked Oct 10, 2014 at 16:17 Pato LocoPato Loco 1,24411 gold badge1414 silver badges3030 bronze badges 3

• Javascript doesn't have a classical inheritance mechanism. – amphetamachine Commented Oct 10, 2014 at 16:19
• Answers to many JS questions can be found on MDN: developer.mozilla/en-US/docs/Web/JavaScript/… – Felix Kling Commented Oct 10, 2014 at 16:53
• There would be no need for 2 options. You can pass one and have the functions use or mutate whatever applies to that specific function. More on prototype and passing arguments to a chain of functions here: stackoverflow./questions/16063394/… – HMR Commented Oct 11, 2014 at 0:27

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1 Answer 1

Sorted by: Reset to default 7

Just call A constructor with this

function B(aOptions, bOptions) {
  A.call(this, aOptions);

  // do stuff with bOptions here...
}

Now to setup the prototype

B.prototype = Object.create(A.prototype, {
  constructor: {
    value: B
  }
});

Now B will have the prototype methods from A.

Any new methods added to B's prototype will not be available to A's prototype

---

There's a couple other tweaks that can make your life easier too.

function A(options) {

  // make `new` optional
  if (!(this instanceof A)) {
    return new A(options);
  }

  // do stuff with options here...
}

And do the same for B

function B(aOptions, bOptions) {

  // make `new` optional
  if (!(this instanceof B)) {
    return new B(aOptions, bOptions);
  }

  // call parent constructor
  A.call(this, aOptions);

  // do stuff with bOptions here...
}

Now you can call A(options) or new A(options) to get the same result.

Same with B, B(aOptions, bOptions) or new B(aOptions, bOptions) will get the same result.