JS new.target vs. instanceof

问题

So I have done some reading on the new.target boolean added in Node 6.x. Here is a simple example of new.target provided on MDN

function Foo() {
  if (!new.target) throw "Foo() must be called with new";
  console.log("Foo instantiated with new");
}

Foo(); // throws "Foo() must be called with new"
new Foo(); // logs "Foo instantiated with new"

But this reads a lot like what I am presently using the below code for

var Foo = function (options) {
  if (!(this instanceof Foo)) {
    return new Foo(options);
  }

  // do stuff here
}

My question is this: Is there any benifit to new.target over the instance of method? I don't particularly see either as more clear. new.target may be a scosche easier to read but only because it has one less set of parens ().

Can anyone provide an insight I am missing? Thanks!

回答1:

Using this instanceof Foo you will check if this instance is a Foo, but you can't ensure that was called with a new. I can just do a thing like this

var foo = new Foo("Test");
var notAFoo = Foo.call(foo, "AnotherWord"); 

And will work fine. Using new.target you can avoid this issues. I suggest you to read this book https://leanpub.com/understandinges6/read

来源：https://stackoverflow.com/questions/37060559/js-new-target-vs-instanceof