Whats the performance impact of setPrototypeOf on a new Object?

Question

The MDN hints that using .setPrototypeOf() will have a bad influence on the future performance of your code.

I also read a few Questions about why changing the [[Prototype]] of an object will lower the performance. But none of the answers really explained whats going on in the background. So I wonder if this also applies for new Objects.

In particular I really like to do things like this:

var MyPrototype = {
    method1 : function(){...},
    method2 : function(){...},
    ...
};

var newObject = Object.setPrototypeOf({
    property : 1,
    property2 : 'text'                 
}, MyPrototype);

Unfortunately you can't do this with Object.create since it doesn't accept a plain object literal.

Does my use of setPrototypeOf also decrease the performance of the executing JS engine?

Answer 1

If you fear (as apparently you should..) the performance impact of using Object.setPrototypeOf(), but want to keep your object creation syntax similar to how your code is structured, try this:

var MyPrototype = {
    method1 : function(){...},
    method2 : function(){...},
    ...
};

var newObject = Object.assign(Object.create(MyPrototype), {
    property : 1,
    property2 : 'text'                 
});