Is it possible to update a library in a backwards compatible manner to incorporate the use of getters?

Question

Is it possible to update a library in a backwards compatible manner to incorporate the use of getters?

Consider a scenario where there is a library containing a function defined as follows:

class Stuff {
  total () {
    return 4; // some calculation could be involved here
  }
}

Now, imagine you want to enhance this by using a getter instead:

class Stuff {
  get total () {
    return 4;
  }
}

How can you make this change in a way that remains backwards compatible? Ensuring that existing code using the function does not break?

stuff.total   // should work with new version
stuff.total() // hopefully this still works

Note: This question delves into the evolution of libraries in a broader sense. The previous one focused on a specific solution and from a call-site perspective.

javascript

Answer 1

Answer №1

It is not advisable to combine a number and a function in stuff.total. This could lead to confusion and difficulty in maintaining the code in the future.

However, there is a workaround that achieves similar functionality:

class Stuff {
  get total () {
    const callable = function ( ) {
      return 4;
    };
    callable[Symbol.toPrimitive] = callable;
    return callable;
  }
}

const stuff = new Stuff;
console.log( stuff.total );
console.log( stuff.total( ) );
console.log( 1 + stuff.total );
console.log( 1 + stuff.total( ) );

// even though stuff.total is technically a function
console.log( typeof stuff.total );
console.log( stuff.total.toString( ) );

// when implicitly coerced to a string, toString is not called:
console.log( '' + stuff.total);
console.log( `${stuff.total}` );

There are some limitations to this approach. The stuff.total getter returns a function, not a number. If used in a context where a primitive value is expected, the function will be invoked, and its return value will be utilized. However, internally it remains a function, as seen in stuff.total.toString( ) or typeof stuff.total.

Answer 2

It is not advisable to combine a number and a function in stuff.total. This could lead to confusion and difficulty in maintaining the code in the future.

However, there is a workaround that achieves similar functionality:

class Stuff {
  get total () {
    const callable = function ( ) {
      return 4;
    };
    callable[Symbol.toPrimitive] = callable;
    return callable;
  }
}

const stuff = new Stuff;
console.log( stuff.total );
console.log( stuff.total( ) );
console.log( 1 + stuff.total );
console.log( 1 + stuff.total( ) );

// even though stuff.total is technically a function
console.log( typeof stuff.total );
console.log( stuff.total.toString( ) );

// when implicitly coerced to a string, toString is not called:
console.log( '' + stuff.total);
console.log( `${stuff.total}` );

There are some limitations to this approach. The stuff.total getter returns a function, not a number. If used in a context where a primitive value is expected, the function will be invoked, and its return value will be utilized. However, internally it remains a function, as seen in stuff.total.toString( ) or typeof stuff.total.

Answer 3

Answer №2

The response leans towards "no", but with a touch of "it depends".

It all boils down to how the current code intends to utilize the outcome. There are scenarios where you can manipulate a getter by returning a function, yet there are other instances where this approach won't suffice.

In your showcased code snippet, a function is returned that yields a straightforward primitive number, adding complexity to the situation. In situations where the result of the getter needs to automatically trigger its .valueOf() method, you can achieve the desired effect by returning a function with an overridden .valueOf().

class Doer {
  get total () {
    var f = function() { return f.valueOf() };
    f.valueOf = function() { return 4 };
    return f
  }
}

const d = new Doer();

const x = 10 + d.total();
const y = 10 + d.total; // The addition forces the .valueOf() evaluation

console.log(x, y);

Nevertheless, d.total remains fundamentally a function rather than the value 4.

If you were to return an object instead, you might be able to emulate it more smoothly by returning an object that inherits from Function.prototype, though effectiveness will heavily rely on practical usage.

Answer 4

The response leans towards "no", but with a touch of "it depends".

It all boils down to how the current code intends to utilize the outcome. There are scenarios where you can manipulate a getter by returning a function, yet there are other instances where this approach won't suffice.

In your showcased code snippet, a function is returned that yields a straightforward primitive number, adding complexity to the situation. In situations where the result of the getter needs to automatically trigger its .valueOf() method, you can achieve the desired effect by returning a function with an overridden .valueOf().

class Doer {
  get total () {
    var f = function() { return f.valueOf() };
    f.valueOf = function() { return 4 };
    return f
  }
}

const d = new Doer();

const x = 10 + d.total();
const y = 10 + d.total; // The addition forces the .valueOf() evaluation

console.log(x, y);

Nevertheless, d.total remains fundamentally a function rather than the value 4.

If you were to return an object instead, you might be able to emulate it more smoothly by returning an object that inherits from Function.prototype, though effectiveness will heavily rely on practical usage.

Is it possible to update a library in a backwards compatible manner to incorporate the use of getters?

Answer №1

Answer №2

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