Function object initializer

💡 Ideas
15

I'm warming up to the idea of a shorthand object-function declaration. Besides allowing to declaratively create functions that have own properties, it would make it simpler to create unbound functions that have no construction behavior.

First some recap on the 3 kinds of function declarations that exist in the language today:

  • function() {} creates a function sensitive to a this arg that can also be called as a constructor
  • () => {} aka arrow functions create a function with a bound this arg that cannot be called as a constructor
  • foo() {} short hand methods (in object literals or class definitions) create a function that is this arg sensitive but cannot be constructed.

The only way to create the latter kind of function today is to use a temporary object literal and extract its short hand method.

Short hand object-functions, { () {} }, would simplify this, while enabling custom prototypes.

const foo = {
  (bar, baz = null) { ... },
  __proto__: CustomFunction.prototype,
  expando: 42,
};

Would be equivalent to:

const foo = Object.setPrototypeOf(
  Object.defineProperties(
    { foo(bar, baz = null) { ... } }.foo,
    Object.getOwnPropertyDescriptors({ expando: 42 }),
  ),
  CustomFunction.prototype,
);
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